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shaka-packager/packager/media/base/container_names.cc

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// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "packager/media/base/container_names.h"
#include <libxml/parser.h>
#include <libxml/tree.h>
#include <stdint.h>
#include <cctype>
#include <limits>
#include "packager/base/logging.h"
#include "packager/media/base/bit_reader.h"
#include "packager/mpd/base/xml/scoped_xml_ptr.h"
namespace edash_packager {
namespace media {
#define TAG(a, b, c, d) \
((static_cast<uint32_t>(static_cast<uint8_t>(a)) << 24) | \
(static_cast<uint8_t>(b) << 16) | (static_cast<uint8_t>(c) << 8) | \
(static_cast<uint8_t>(d)))
#define RCHECK(x) \
do { \
if (!(x)) \
return false; \
} while (0)
#define UTF8_BYTE_ORDER_MARK "\xef\xbb\xbf"
// Helper function to read 2 bytes (16 bits, big endian) from a buffer.
static int Read16(const uint8_t* p) {
return p[0] << 8 | p[1];
}
// Helper function to read 3 bytes (24 bits, big endian) from a buffer.
static uint32_t Read24(const uint8_t* p) {
return p[0] << 16 | p[1] << 8 | p[2];
}
// Helper function to read 4 bytes (32 bits, big endian) from a buffer.
static uint32_t Read32(const uint8_t* p) {
return p[0] << 24 | p[1] << 16 | p[2] << 8 | p[3];
}
// Helper function to read 4 bytes (32 bits, little endian) from a buffer.
static uint32_t Read32LE(const uint8_t* p) {
return p[3] << 24 | p[2] << 16 | p[1] << 8 | p[0];
}
// Helper function to do buffer comparisons with a string without going off the
// end of the buffer.
static bool StartsWith(const uint8_t* buffer,
size_t buffer_size,
const char* prefix) {
size_t prefix_size = strlen(prefix);
return (prefix_size <= buffer_size &&
memcmp(buffer, prefix, prefix_size) == 0);
}
// Helper function to do buffer comparisons with another buffer (to allow for
// embedded \0 in the comparison) without going off the end of the buffer.
static bool StartsWith(const uint8_t* buffer,
size_t buffer_size,
const uint8_t* prefix,
size_t prefix_size) {
return (prefix_size <= buffer_size &&
memcmp(buffer, prefix, prefix_size) == 0);
}
// Helper function to read up to 64 bits from a bit stream.
static uint64_t ReadBits(BitReader* reader, int num_bits) {
DCHECK_GE(reader->bits_available(), num_bits);
DCHECK((num_bits > 0) && (num_bits <= 64));
uint64_t value;
reader->ReadBits(num_bits, &value);
return value;
}
const int kAc3FrameSizeTable[38][3] = {
{ 128, 138, 192 }, { 128, 140, 192 }, { 160, 174, 240 }, { 160, 176, 240 },
{ 192, 208, 288 }, { 192, 210, 288 }, { 224, 242, 336 }, { 224, 244, 336 },
{ 256, 278, 384 }, { 256, 280, 384 }, { 320, 348, 480 }, { 320, 350, 480 },
{ 384, 416, 576 }, { 384, 418, 576 }, { 448, 486, 672 }, { 448, 488, 672 },
{ 512, 556, 768 }, { 512, 558, 768 }, { 640, 696, 960 }, { 640, 698, 960 },
{ 768, 834, 1152 }, { 768, 836, 1152 }, { 896, 974, 1344 },
{ 896, 976, 1344 }, { 1024, 1114, 1536 }, { 1024, 1116, 1536 },
{ 1280, 1392, 1920 }, { 1280, 1394, 1920 }, { 1536, 1670, 2304 },
{ 1536, 1672, 2304 }, { 1792, 1950, 2688 }, { 1792, 1952, 2688 },
{ 2048, 2228, 3072 }, { 2048, 2230, 3072 }, { 2304, 2506, 3456 },
{ 2304, 2508, 3456 }, { 2560, 2768, 3840 }, { 2560, 2770, 3840 }
};
// Checks for an ADTS AAC container.
static bool CheckAac(const uint8_t* buffer, int buffer_size) {
// Audio Data Transport Stream (ADTS) header is 7 or 9 bytes
// (from http://wiki.multimedia.cx/index.php?title=ADTS)
RCHECK(buffer_size > 6);
int offset = 0;
while (offset + 6 < buffer_size) {
BitReader reader(buffer + offset, 6);
// Syncword must be 0xfff.
RCHECK(ReadBits(&reader, 12) == 0xfff);
// Skip MPEG version.
reader.SkipBits(1);
// Layer is always 0.
RCHECK(ReadBits(&reader, 2) == 0);
// Skip protection + profile.
reader.SkipBits(1 + 2);
// Check sampling frequency index.
RCHECK(ReadBits(&reader, 4) != 15); // Forbidden.
// Skip private stream, channel configuration, originality, home,
// copyrighted stream, and copyright_start.
reader.SkipBits(1 + 3 + 1 + 1 + 1 + 1);
// Get frame length (includes header).
int size = ReadBits(&reader, 13);
RCHECK(size > 0);
offset += size;
}
return true;
}
const uint16_t kAc3SyncWord = 0x0b77;
// Checks for an AC3 container.
static bool CheckAc3(const uint8_t* buffer, int buffer_size) {
// Reference: ATSC Standard: Digital Audio Compression (AC-3, E-AC-3)
// Doc. A/52:2012
// (http://www.atsc.org/cms/standards/A52-2012(12-17).pdf)
// AC3 container looks like syncinfo | bsi | audblk * 6 | aux | check.
RCHECK(buffer_size > 6);
int offset = 0;
while (offset + 6 < buffer_size) {
BitReader reader(buffer + offset, 6);
// Check syncinfo.
RCHECK(ReadBits(&reader, 16) == kAc3SyncWord);
// Skip crc1.
reader.SkipBits(16);
// Verify fscod.
int sample_rate_code = ReadBits(&reader, 2);
RCHECK(sample_rate_code != 3); // Reserved.
// Verify frmsizecod.
int frame_size_code = ReadBits(&reader, 6);
RCHECK(frame_size_code < 38); // Undefined.
// Verify bsid.
RCHECK(ReadBits(&reader, 5) < 10); // Normally 8 or 6, 16 used by EAC3.
offset += kAc3FrameSizeTable[frame_size_code][sample_rate_code];
}
return true;
}
// Checks for an EAC3 container (very similar to AC3)
static bool CheckEac3(const uint8_t* buffer, int buffer_size) {
// Reference: ATSC Standard: Digital Audio Compression (AC-3, E-AC-3)
// Doc. A/52:2012
// (http://www.atsc.org/cms/standards/A52-2012(12-17).pdf)
// EAC3 container looks like syncinfo | bsi | audfrm | audblk* | aux | check.
RCHECK(buffer_size > 6);
int offset = 0;
while (offset + 6 < buffer_size) {
BitReader reader(buffer + offset, 6);
// Check syncinfo.
RCHECK(ReadBits(&reader, 16) == kAc3SyncWord);
// Verify strmtyp.
RCHECK(ReadBits(&reader, 2) != 3);
// Skip substreamid.
reader.SkipBits(3);
// Get frmsize. Include syncinfo size and convert to bytes.
int frame_size = (ReadBits(&reader, 11) + 1) * 2;
RCHECK(frame_size >= 7);
// Skip fscod, fscod2, acmod, and lfeon.
reader.SkipBits(2 + 2 + 3 + 1);
// Verify bsid.
int bit_stream_id = ReadBits(&reader, 5);
RCHECK(bit_stream_id >= 11 && bit_stream_id <= 16);
offset += frame_size;
}
return true;
}
// Additional checks for a BINK container.
static bool CheckBink(const uint8_t* buffer, int buffer_size) {
// Reference: http://wiki.multimedia.cx/index.php?title=Bink_Container
RCHECK(buffer_size >= 44);
// Verify number of frames specified.
RCHECK(Read32LE(buffer + 8) > 0);
// Verify width in range.
int width = Read32LE(buffer + 20);
RCHECK(width > 0 && width <= 32767);
// Verify height in range.
int height = Read32LE(buffer + 24);
RCHECK(height > 0 && height <= 32767);
// Verify frames per second specified.
RCHECK(Read32LE(buffer + 28) > 0);
// Verify video frames per second specified.
RCHECK(Read32LE(buffer + 32) > 0);
// Number of audio tracks must be 256 or less.
return (Read32LE(buffer + 40) <= 256);
}
// Additional checks for a CAF container.
static bool CheckCaf(const uint8_t* buffer, int buffer_size) {
// Reference: Apple Core Audio Format Specification 1.0
// (https://developer.apple.com/library/mac/#documentation/MusicAudio/Reference/CAFSpec/CAF_spec/CAF_spec.html)
RCHECK(buffer_size >= 52);
BitReader reader(buffer, buffer_size);
// mFileType should be "caff".
RCHECK(ReadBits(&reader, 32) == TAG('c', 'a', 'f', 'f'));
// mFileVersion should be 1.
RCHECK(ReadBits(&reader, 16) == 1);
// Skip mFileFlags.
reader.SkipBits(16);
// First chunk should be Audio Description chunk, size 32l.
RCHECK(ReadBits(&reader, 32) == TAG('d', 'e', 's', 'c'));
RCHECK(ReadBits(&reader, 64) == 32);
// CAFAudioFormat.mSampleRate(float64) not 0
RCHECK(ReadBits(&reader, 64) != 0);
// CAFAudioFormat.mFormatID not 0
RCHECK(ReadBits(&reader, 32) != 0);
// Skip CAFAudioFormat.mBytesPerPacket and mFramesPerPacket.
reader.SkipBits(32 + 32);
// CAFAudioFormat.mChannelsPerFrame not 0
RCHECK(ReadBits(&reader, 32) != 0);
return true;
}
static bool kSamplingFrequencyValid[16] = { false, true, true, true, false,
false, true, true, true, false,
false, true, true, true, false,
false };
static bool kExtAudioIdValid[8] = { true, false, true, false, false, false,
true, false };
// Additional checks for a DTS container.
static bool CheckDts(const uint8_t* buffer, int buffer_size) {
// Reference: ETSI TS 102 114 V1.3.1 (2011-08)
// (http://www.etsi.org/deliver/etsi_ts/102100_102199/102114/01.03.01_60/ts_102114v010301p.pdf)
RCHECK(buffer_size > 11);
int offset = 0;
while (offset + 11 < buffer_size) {
BitReader reader(buffer + offset, 11);
// Verify sync word.
RCHECK(ReadBits(&reader, 32) == 0x7ffe8001);
// Skip frame type and deficit sample count.
reader.SkipBits(1 + 5);
// Verify CRC present flag.
RCHECK(ReadBits(&reader, 1) == 0); // CPF must be 0.
// Verify number of PCM sample blocks.
RCHECK(ReadBits(&reader, 7) >= 5);
// Verify primary frame byte size.
int frame_size = ReadBits(&reader, 14);
RCHECK(frame_size >= 95);
// Skip audio channel arrangement.
reader.SkipBits(6);
// Verify core audio sampling frequency is an allowed value.
RCHECK(kSamplingFrequencyValid[ReadBits(&reader, 4)]);
// Verify transmission bit rate is valid.
RCHECK(ReadBits(&reader, 5) <= 25);
// Verify reserved field is 0.
RCHECK(ReadBits(&reader, 1) == 0);
// Skip dynamic range flag, time stamp flag, auxiliary data flag, and HDCD.
reader.SkipBits(1 + 1 + 1 + 1);
// Verify extension audio descriptor flag is an allowed value.
RCHECK(kExtAudioIdValid[ReadBits(&reader, 3)]);
// Skip extended coding flag and audio sync word insertion flag.
reader.SkipBits(1 + 1);
// Verify low frequency effects flag is an allowed value.
RCHECK(ReadBits(&reader, 2) != 3);
offset += frame_size + 1;
}
return true;
}
// Checks for a DV container.
static bool CheckDV(const uint8_t* buffer, int buffer_size) {
// Reference: SMPTE 314M (Annex A has differences with IEC 61834).
// (http://standards.smpte.org/content/978-1-61482-454-1/st-314-2005/SEC1.body.pdf)
RCHECK(buffer_size > 11);
int offset = 0;
int current_sequence_number = -1;
int last_block_number[6];
while (offset + 11 < buffer_size) {
BitReader reader(buffer + offset, 11);
// Decode ID data. Sections 5, 6, and 7 are reserved.
int section = ReadBits(&reader, 3);
RCHECK(section < 5);
// Next bit must be 1.
RCHECK(ReadBits(&reader, 1) == 1);
// Skip arbitrary bits.
reader.SkipBits(4);
int sequence_number = ReadBits(&reader, 4);
// Skip FSC.
reader.SkipBits(1);
// Next 3 bits must be 1.
RCHECK(ReadBits(&reader, 3) == 7);
int block_number = ReadBits(&reader, 8);
if (section == 0) { // Header.
// Validate the reserved bits in the next 8 bytes.
reader.SkipBits(1);
RCHECK(ReadBits(&reader, 1) == 0);
RCHECK(ReadBits(&reader, 11) == 0x7ff);
reader.SkipBits(4);
RCHECK(ReadBits(&reader, 4) == 0xf);
reader.SkipBits(4);
RCHECK(ReadBits(&reader, 4) == 0xf);
reader.SkipBits(4);
RCHECK(ReadBits(&reader, 4) == 0xf);
reader.SkipBits(3);
RCHECK(ReadBits(&reader, 24) == 0xffffff);
current_sequence_number = sequence_number;
for (size_t i = 0; i < arraysize(last_block_number); ++i)
last_block_number[i] = -1;
} else {
// Sequence number must match (this will also fail if no header seen).
RCHECK(sequence_number == current_sequence_number);
// Block number should be increasing.
RCHECK(block_number > last_block_number[section]);
last_block_number[section] = block_number;
}
// Move to next block.
offset += 80;
}
return true;
}
// Checks for a GSM container.
static bool CheckGsm(const uint8_t* buffer, int buffer_size) {
// Reference: ETSI EN 300 961 V8.1.1
// (http://www.etsi.org/deliver/etsi_en/300900_300999/300961/08.01.01_60/en_300961v080101p.pdf)
// also http://tools.ietf.org/html/rfc3551#page-24
// GSM files have a 33 byte block, only first 4 bits are fixed.
RCHECK(buffer_size >= 1024); // Need enough data to do a decent check.
int offset = 0;
while (offset < buffer_size) {
// First 4 bits of each block are xD.
RCHECK((buffer[offset] & 0xf0) == 0xd0);
offset += 33;
}
return true;
}
// Advance to the first set of |num_bits| bits that match |start_code|. |offset|
// is the current location in the buffer, and is updated. |bytes_needed| is the
// number of bytes that must remain in the buffer when |start_code| is found.
// Returns true if start_code found (and enough space in the buffer after it),
// false otherwise.
static bool AdvanceToStartCode(const uint8_t* buffer,
int buffer_size,
int* offset,
int bytes_needed,
int num_bits,
uint32_t start_code) {
DCHECK_GE(bytes_needed, 3);
DCHECK_LE(num_bits, 24); // Only supports up to 24 bits.
// Create a mask to isolate |num_bits| bits, once shifted over.
uint32_t bits_to_shift = 24 - num_bits;
uint32_t mask = (1 << num_bits) - 1;
while (*offset + bytes_needed < buffer_size) {
uint32_t next = Read24(buffer + *offset);
if (((next >> bits_to_shift) & mask) == start_code)
return true;
++(*offset);
}
return false;
}
// Checks for an H.261 container.
static bool CheckH261(const uint8_t* buffer, int buffer_size) {
// Reference: ITU-T Recommendation H.261 (03/1993)
// (http://www.itu.int/rec/T-REC-H.261-199303-I/en)
RCHECK(buffer_size > 16);
int offset = 0;
bool seen_start_code = false;
while (true) {
// Advance to picture_start_code, if there is one.
if (!AdvanceToStartCode(buffer, buffer_size, &offset, 4, 20, 0x10)) {
// No start code found (or off end of buffer), so success if
// there was at least one valid header.
return seen_start_code;
}
// Now verify the block. AdvanceToStartCode() made sure that there are
// at least 4 bytes remaining in the buffer.
BitReader reader(buffer + offset, buffer_size - offset);
RCHECK(ReadBits(&reader, 20) == 0x10);
// Skip the temporal reference and PTYPE.
reader.SkipBits(5 + 6);
// Skip any extra insertion information. Since this is open-ended, if we run
// out of bits assume that the buffer is correctly formatted.
int extra = ReadBits(&reader, 1);
while (extra == 1) {
if (!reader.SkipBits(8))
return seen_start_code;
if (!reader.ReadBits(1, &extra))
return seen_start_code;
}
// Next should be a Group of Blocks start code. Again, if we run out of
// bits, then assume that the buffer up to here is correct, and the buffer
// just happened to end in the middle of a header.
int next;
if (!reader.ReadBits(16, &next))
return seen_start_code;
RCHECK(next == 1);
// Move to the next block.
seen_start_code = true;
offset += 4;
}
}
// Checks for an H.263 container.
static bool CheckH263(const uint8_t* buffer, int buffer_size) {
// Reference: ITU-T Recommendation H.263 (01/2005)
// (http://www.itu.int/rec/T-REC-H.263-200501-I/en)
// header is PSC(22b) + TR(8b) + PTYPE(8+b).
RCHECK(buffer_size > 16);
int offset = 0;
bool seen_start_code = false;
while (true) {
// Advance to picture_start_code, if there is one.
if (!AdvanceToStartCode(buffer, buffer_size, &offset, 9, 22, 0x20)) {
// No start code found (or off end of buffer), so success if
// there was at least one valid header.
return seen_start_code;
}
// Now verify the block. AdvanceToStartCode() made sure that there are
// at least 9 bytes remaining in the buffer.
BitReader reader(buffer + offset, 9);
RCHECK(ReadBits(&reader, 22) == 0x20);
// Skip the temporal reference.
reader.SkipBits(8);
// Verify that the first 2 bits of PTYPE are 10b.
RCHECK(ReadBits(&reader, 2) == 2);
// Skip the split screen indicator, document camera indicator, and full
// picture freeze release.
reader.SkipBits(1 + 1 + 1);
// Verify Source Format.
int format = ReadBits(&reader, 3);
RCHECK(format != 0 && format != 6); // Forbidden or reserved.
if (format == 7) {
// Verify full extended PTYPE.
int ufep = ReadBits(&reader, 3);
if (ufep == 1) {
// Verify the optional part of PLUSPTYPE.
format = ReadBits(&reader, 3);
RCHECK(format != 0 && format != 7); // Reserved.
reader.SkipBits(11);
// Next 4 bits should be b1000.
RCHECK(ReadBits(&reader, 4) == 8); // Not allowed.
} else {
RCHECK(ufep == 0); // Only 0 and 1 allowed.
}
// Verify picture type code is not a reserved value.
int picture_type_code = ReadBits(&reader, 3);
RCHECK(picture_type_code != 6 && picture_type_code != 7); // Reserved.
// Skip picture resampling mode, reduced resolution mode,
// and rounding type.
reader.SkipBits(1 + 1 + 1);
// Next 3 bits should be b001.
RCHECK(ReadBits(&reader, 3) == 1); // Not allowed.
}
// Move to the next block.
seen_start_code = true;
offset += 9;
}
}
// Checks for an H.264 container.
static bool CheckH264(const uint8_t* buffer, int buffer_size) {
// Reference: ITU-T Recommendation H.264 (01/2012)
// (http://www.itu.int/rec/T-REC-H.264)
// Section B.1: Byte stream NAL unit syntax and semantics.
RCHECK(buffer_size > 4);
int offset = 0;
int parameter_count = 0;
while (true) {
// Advance to picture_start_code, if there is one.
if (!AdvanceToStartCode(buffer, buffer_size, &offset, 4, 24, 1)) {
// No start code found (or off end of buffer), so success if
// there was at least one valid header.
return parameter_count > 0;
}
// Now verify the block. AdvanceToStartCode() made sure that there are
// at least 4 bytes remaining in the buffer.
BitReader reader(buffer + offset, 4);
RCHECK(ReadBits(&reader, 24) == 1);
// Verify forbidden_zero_bit.
RCHECK(ReadBits(&reader, 1) == 0);
// Extract nal_ref_idc and nal_unit_type.
int nal_ref_idc = ReadBits(&reader, 2);
int nal_unit_type = ReadBits(&reader, 5);
switch (nal_unit_type) {
case 5: // Coded slice of an IDR picture.
RCHECK(nal_ref_idc != 0);
break;
case 6: // Supplemental enhancement information (SEI).
case 9: // Access unit delimiter.
case 10: // End of sequence.
case 11: // End of stream.
case 12: // Filler data.
RCHECK(nal_ref_idc == 0);
break;
case 7: // Sequence parameter set.
case 8: // Picture parameter set.
++parameter_count;
break;
}
// Skip the current start_code_prefix and move to the next.
offset += 4;
}
}
static const char kHlsSignature[] = "#EXTM3U";
static const char kHls1[] = "#EXT-X-STREAM-INF:";
static const char kHls2[] = "#EXT-X-TARGETDURATION:";
static const char kHls3[] = "#EXT-X-MEDIA-SEQUENCE:";
// Additional checks for a HLS container.
static bool CheckHls(const uint8_t* buffer, int buffer_size) {
// HLS is simply a play list used for Apple HTTP Live Streaming.
// Reference: Apple HTTP Live Streaming Overview
// (http://goo.gl/MIwxj)
if (StartsWith(buffer, buffer_size, kHlsSignature)) {
// Need to find "#EXT-X-STREAM-INF:", "#EXT-X-TARGETDURATION:", or
// "#EXT-X-MEDIA-SEQUENCE:" somewhere in the buffer. Other playlists (like
// WinAmp) only have additional lines with #EXTINF
// (http://en.wikipedia.org/wiki/M3U).
int offset = strlen(kHlsSignature);
while (offset < buffer_size) {
if (buffer[offset] == '#') {
if (StartsWith(buffer + offset, buffer_size - offset, kHls1) ||
StartsWith(buffer + offset, buffer_size - offset, kHls2) ||
StartsWith(buffer + offset, buffer_size - offset, kHls3)) {
return true;
}
}
++offset;
}
}
return false;
}
// Checks for a MJPEG stream.
static bool CheckMJpeg(const uint8_t* buffer, int buffer_size) {
// Reference: ISO/IEC 10918-1 : 1993(E), Annex B
// (http://www.w3.org/Graphics/JPEG/itu-t81.pdf)
RCHECK(buffer_size >= 16);
int offset = 0;
int last_restart = -1;
int num_codes = 0;
while (offset + 5 < buffer_size) {
// Marker codes are always a two byte code with the first byte xFF.
RCHECK(buffer[offset] == 0xff);
uint8_t code = buffer[offset + 1];
RCHECK(code >= 0xc0 || code == 1);
// Skip sequences of xFF.
if (code == 0xff) {
++offset;
continue;
}
// Success if the next marker code is EOI (end of image)
if (code == 0xd9)
return true;
// Check remaining codes.
if (code == 0xd8 || code == 1) {
// SOI (start of image) / TEM (private use). No other data with header.
offset += 2;
} else if (code >= 0xd0 && code <= 0xd7) {
// RST (restart) codes must be in sequence. No other data with header.
int restart = code & 0x07;
if (last_restart >= 0)
RCHECK(restart == (last_restart + 1) % 8);
last_restart = restart;
offset += 2;
} else {
// All remaining marker codes are followed by a length of the header.
int length = Read16(buffer + offset + 2) + 2;
// Special handling of SOS (start of scan) marker since the entropy
// coded data follows the SOS. Any xFF byte in the data block must be
// followed by x00 in the data.
if (code == 0xda) {
int number_components = buffer[offset + 4];
RCHECK(length == 8 + 2 * number_components);
// Advance to the next marker.
offset += length;
while (offset + 2 < buffer_size) {
if (buffer[offset] == 0xff && buffer[offset + 1] != 0)
break;
++offset;
}
} else {
// Skip over the marker data for the other marker codes.
offset += length;
}
}
++num_codes;
}
return (num_codes > 1);
}
enum Mpeg2StartCodes {
PROGRAM_END_CODE = 0xb9,
PACK_START_CODE = 0xba
};
// Checks for a MPEG2 Program Stream.
static bool CheckMpeg2ProgramStream(const uint8_t* buffer, int buffer_size) {
// Reference: ISO/IEC 13818-1 : 2000 (E) / ITU-T Rec. H.222.0 (2000 E).
RCHECK(buffer_size > 14);
int offset = 0;
while (offset + 14 < buffer_size) {
BitReader reader(buffer + offset, 14);
// Must start with pack_start_code.
RCHECK(ReadBits(&reader, 24) == 1);
RCHECK(ReadBits(&reader, 8) == PACK_START_CODE);
// Determine MPEG version (MPEG1 has b0010, while MPEG2 has b01).
int mpeg_version = ReadBits(&reader, 2);
if (mpeg_version == 0) {
// MPEG1, 10 byte header
// Validate rest of version code
RCHECK(ReadBits(&reader, 2) == 2);
} else {
RCHECK(mpeg_version == 1);
}
// Skip system_clock_reference_base [32..30].
reader.SkipBits(3);
// Verify marker bit.
RCHECK(ReadBits(&reader, 1) == 1);
// Skip system_clock_reference_base [29..15].
reader.SkipBits(15);
// Verify next marker bit.
RCHECK(ReadBits(&reader, 1) == 1);
// Skip system_clock_reference_base [14..0].
reader.SkipBits(15);
// Verify next marker bit.
RCHECK(ReadBits(&reader, 1) == 1);
if (mpeg_version == 0) {
// Verify second marker bit.
RCHECK(ReadBits(&reader, 1) == 1);
// Skip mux_rate.
reader.SkipBits(22);
// Verify next marker bit.
RCHECK(ReadBits(&reader, 1) == 1);
// Update offset to be after this header.
offset += 12;
} else {
// Must be MPEG2.
// Skip program_mux_rate.
reader.SkipBits(22);
// Verify pair of marker bits.
RCHECK(ReadBits(&reader, 2) == 3);
// Skip reserved.
reader.SkipBits(5);
// Update offset to be after this header.
int pack_stuffing_length = ReadBits(&reader, 3);
offset += 14 + pack_stuffing_length;
}
// Check for system headers and PES_packets.
while (offset + 6 < buffer_size && Read24(buffer + offset) == 1) {
// Next 8 bits determine stream type.
int stream_id = buffer[offset + 3];
// Some stream types are reserved and shouldn't occur.
if (mpeg_version == 0)
RCHECK(stream_id != 0xbc && stream_id < 0xf0);
else
RCHECK(stream_id != 0xfc && stream_id != 0xfd && stream_id != 0xfe);
// Some stream types are used for pack headers.
if (stream_id == PACK_START_CODE) // back to outer loop.
break;
if (stream_id == PROGRAM_END_CODE) // end of stream.
return true;
int pes_length = Read16(buffer + offset + 4);
RCHECK(pes_length > 0);
offset = offset + 6 + pes_length;
}
}
// Success as we are off the end of the buffer and liked everything
// in the buffer.
return true;
}
const uint8_t kMpeg2SyncWord = 0x47;
// Checks for a MPEG2 Transport Stream.
static bool CheckMpeg2TransportStream(const uint8_t* buffer, int buffer_size) {
// Spec: ISO/IEC 13818-1 : 2000 (E) / ITU-T Rec. H.222.0 (2000 E).
// Normal packet size is 188 bytes. However, some systems add various error
// correction data at the end, resulting in packet of length 192/204/208
// (https://en.wikipedia.org/wiki/MPEG_transport_stream). Determine the
// length with the first packet.
RCHECK(buffer_size >= 250); // Want more than 1 packet to check.
int offset = 0;
int packet_length = -1;
while (buffer[offset] != kMpeg2SyncWord && offset < 20) {
// Skip over any header in the first 20 bytes.
++offset;
}
while (offset + 6 < buffer_size) {
BitReader reader(buffer + offset, 6);
// Must start with sync byte.
RCHECK(ReadBits(&reader, 8) == kMpeg2SyncWord);
// Skip transport_error_indicator, payload_unit_start_indicator, and
// transport_priority.
reader.SkipBits(1 + 1 + 1);
// Verify the pid is not a reserved value.
int pid = ReadBits(&reader, 13);
RCHECK(pid < 3 || pid > 15);
// Skip transport_scrambling_control.
reader.SkipBits(2);
// Adaptation_field_control can not be 0.
int adaptation_field_control = ReadBits(&reader, 2);
RCHECK(adaptation_field_control != 0);
// If there is an adaptation_field, verify it.
if (adaptation_field_control >= 2) {
// Skip continuity_counter.
reader.SkipBits(4);
// Get adaptation_field_length and verify it.
int adaptation_field_length = ReadBits(&reader, 8);
if (adaptation_field_control == 2)
RCHECK(adaptation_field_length == 183);
else
RCHECK(adaptation_field_length <= 182);
}
// Attempt to determine the packet length on the first packet.
if (packet_length < 0) {
if (buffer[offset + 188] == kMpeg2SyncWord)
packet_length = 188;
else if (buffer[offset + 192] == kMpeg2SyncWord)
packet_length = 192;
else if (buffer[offset + 204] == kMpeg2SyncWord)
packet_length = 204;
else
packet_length = 208;
}
offset += packet_length;
}
return true;
}
enum Mpeg4StartCodes {
VISUAL_OBJECT_SEQUENCE_START_CODE = 0xb0,
VISUAL_OBJECT_SEQUENCE_END_CODE = 0xb1,
VISUAL_OBJECT_START_CODE = 0xb5,
VOP_START_CODE = 0xb6
};
// Checks for a raw MPEG4 bitstream container.
static bool CheckMpeg4BitStream(const uint8_t* buffer, int buffer_size) {
// Defined in ISO/IEC 14496-2:2001.
// However, no length ... simply scan for start code values.
// Note tags are very similar to H.264.
RCHECK(buffer_size > 4);
int offset = 0;
int sequence_start_count = 0;
int sequence_end_count = 0;
int visual_object_count = 0;
int vop_count = 0;
while (true) {
// Advance to start_code, if there is one.
if (!AdvanceToStartCode(buffer, buffer_size, &offset, 6, 24, 1)) {
// Not a complete sequence in memory, so return true if we've seen a
// visual_object_sequence_start_code and a visual_object_start_code.
return (sequence_start_count > 0 && visual_object_count > 0);
}
// Now verify the block. AdvanceToStartCode() made sure that there are
// at least 6 bytes remaining in the buffer.
BitReader reader(buffer + offset, 6);
RCHECK(ReadBits(&reader, 24) == 1);
int start_code = ReadBits(&reader, 8);
RCHECK(start_code < 0x30 || start_code > 0xaf); // 30..AF and
RCHECK(start_code < 0xb7 || start_code > 0xb9); // B7..B9 reserved
switch (start_code) {
case VISUAL_OBJECT_SEQUENCE_START_CODE: {
++sequence_start_count;
// Verify profile in not one of many reserved values.
int profile = ReadBits(&reader, 8);
RCHECK(profile > 0);
RCHECK(profile < 0x04 || profile > 0x10);
RCHECK(profile < 0x13 || profile > 0x20);
RCHECK(profile < 0x23 || profile > 0x31);
RCHECK(profile < 0x35 || profile > 0x41);
RCHECK(profile < 0x43 || profile > 0x60);
RCHECK(profile < 0x65 || profile > 0x70);
RCHECK(profile < 0x73 || profile > 0x80);
RCHECK(profile < 0x83 || profile > 0x90);
RCHECK(profile < 0x95 || profile > 0xa0);
RCHECK(profile < 0xa4 || profile > 0xb0);
RCHECK(profile < 0xb5 || profile > 0xc0);
RCHECK(profile < 0xc3 || profile > 0xd0);
RCHECK(profile < 0xe4);
break;
}
case VISUAL_OBJECT_SEQUENCE_END_CODE:
RCHECK(++sequence_end_count == sequence_start_count);
break;
case VISUAL_OBJECT_START_CODE: {
++visual_object_count;
if (ReadBits(&reader, 1) == 1) {
int visual_object_verid = ReadBits(&reader, 4);
RCHECK(visual_object_verid > 0 && visual_object_verid < 3);
RCHECK(ReadBits(&reader, 3) != 0);
}
int visual_object_type = ReadBits(&reader, 4);
RCHECK(visual_object_type > 0 && visual_object_type < 6);
break;
}
case VOP_START_CODE:
RCHECK(++vop_count <= visual_object_count);
break;
}
// Skip this block.
offset += 6;
}
}
// Additional checks for a MOV/QuickTime/MPEG4 container.
static bool CheckMov(const uint8_t* buffer, int buffer_size) {
// Reference: ISO/IEC 14496-12:2005(E).
// (http://standards.iso.org/ittf/PubliclyAvailableStandards/c061988_ISO_IEC_14496-12_2012.zip)
RCHECK(buffer_size > 8);
int offset = 0;
while (offset + 8 < buffer_size) {
int atomsize = Read32(buffer + offset);
uint32_t atomtype = Read32(buffer + offset + 4);
// Only need to check for ones that are valid at the top level.
switch (atomtype) {
case TAG('f','t','y','p'):
case TAG('p','d','i','n'):
case TAG('m','o','o','v'):
case TAG('m','o','o','f'):
case TAG('m','f','r','a'):
case TAG('m','d','a','t'):
case TAG('f','r','e','e'):
case TAG('s','k','i','p'):
case TAG('m','e','t','a'):
case TAG('m','e','c','o'):
case TAG('s','t','y','p'):
case TAG('s','i','d','x'):
case TAG('s','s','i','x'):
case TAG('p','r','f','t'):
case TAG('b','l','o','c'):
break;
default:
return false;
}
if (atomsize == 1) {
// Indicates that the length is the next 64bits.
if (offset + 16 > buffer_size)
break;
if (Read32(buffer + offset + 8) != 0)
break; // Offset is way past buffer size.
atomsize = Read32(buffer + offset + 12);
}
if (atomsize <= 0)
break; // Indicates the last atom or length too big.
offset += atomsize;
}
return true;
}
enum MPEGVersion {
VERSION_25 = 0,
VERSION_RESERVED,
VERSION_2,
VERSION_1
};
enum MPEGLayer {
L_RESERVED = 0,
LAYER_3,
LAYER_2,
LAYER_1
};
static int kSampleRateTable[4][4] = { { 11025, 12000, 8000, 0 }, // v2.5
{ 0, 0, 0, 0 }, // not used
{ 22050, 24000, 16000, 0 }, // v2
{ 44100, 48000, 32000, 0 } // v1
};
static int kBitRateTableV1L1[16] = { 0, 32, 64, 96, 128, 160, 192, 224, 256,
288, 320, 352, 384, 416, 448, 0 };
static int kBitRateTableV1L2[16] = { 0, 32, 48, 56, 64, 80, 96, 112, 128, 160,
192, 224, 256, 320, 384, 0 };
static int kBitRateTableV1L3[16] = { 0, 32, 40, 48, 56, 64, 80, 96, 112, 128,
160, 192, 224, 256, 320, 0 };
static int kBitRateTableV2L1[16] = { 0, 32, 48, 56, 64, 80, 96, 112, 128, 144,
160, 176, 192, 224, 256, 0 };
static int kBitRateTableV2L23[16] = { 0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,
112, 128, 144, 160, 0 };
static bool ValidMpegAudioFrameHeader(const uint8_t* header,
int header_size,
int* framesize) {
// Reference: http://mpgedit.org/mpgedit/mpeg_format/mpeghdr.htm.
DCHECK_GE(header_size, 4);
*framesize = 0;
BitReader reader(header, 4); // Header can only be 4 bytes long.
// Verify frame sync (11 bits) are all set.
RCHECK(ReadBits(&reader, 11) == 0x7ff);
// Verify MPEG audio version id.
int version = ReadBits(&reader, 2);
RCHECK(version != 1); // Reserved.
// Verify layer.
int layer = ReadBits(&reader, 2);
RCHECK(layer != 0);
// Skip protection bit.
reader.SkipBits(1);
// Verify bitrate index.
int bitrate_index = ReadBits(&reader, 4);
RCHECK(bitrate_index != 0xf);
// Verify sampling rate frequency index.
int sampling_index = ReadBits(&reader, 2);
RCHECK(sampling_index != 3);
// Get padding bit.
int padding = ReadBits(&reader, 1);
// Frame size:
// For Layer I files = (12 * BitRate / SampleRate + Padding) * 4
// For others = 144 * BitRate / SampleRate + Padding
// Unfortunately, BitRate and SampleRate are coded.
int sampling_rate = kSampleRateTable[version][sampling_index];
int bitrate;
if (version == VERSION_1) {
if (layer == LAYER_1)
bitrate = kBitRateTableV1L1[bitrate_index];
else if (layer == LAYER_2)
bitrate = kBitRateTableV1L2[bitrate_index];
else
bitrate = kBitRateTableV1L3[bitrate_index];
} else {
if (layer == LAYER_1)
bitrate = kBitRateTableV2L1[bitrate_index];
else
bitrate = kBitRateTableV2L23[bitrate_index];
}
if (layer == LAYER_1)
*framesize = ((12000 * bitrate) / sampling_rate + padding) * 4;
else
*framesize = (144000 * bitrate) / sampling_rate + padding;
return (bitrate > 0 && sampling_rate > 0);
}
// Extract a size encoded the MP3 way.
static int GetMp3HeaderSize(const uint8_t* buffer, int buffer_size) {
DCHECK_GE(buffer_size, 9);
int size = ((buffer[6] & 0x7f) << 21) + ((buffer[7] & 0x7f) << 14) +
((buffer[8] & 0x7f) << 7) + (buffer[9] & 0x7f) + 10;
if (buffer[5] & 0x10) // Footer added?
size += 10;
return size;
}
// Additional checks for a MP3 container.
static bool CheckMp3(const uint8_t* buffer, int buffer_size, bool seenHeader) {
RCHECK(buffer_size >= 10); // Must be enough to read the initial header.
int framesize;
int numSeen = 0;
int offset = 0;
if (seenHeader) {
offset = GetMp3HeaderSize(buffer, buffer_size);
} else {
// Skip over leading 0's.
while (offset < buffer_size && buffer[offset] == 0)
++offset;
}
while (offset + 3 < buffer_size) {
RCHECK(ValidMpegAudioFrameHeader(
buffer + offset, buffer_size - offset, &framesize));
// Have we seen enough valid headers?
if (++numSeen > 10)
return true;
offset += framesize;
}
// Off the end of the buffer, return success if a few valid headers seen.
return numSeen > 2;
}
// Check that the next characters in |buffer| represent a number. The format
// accepted is optional whitespace followed by 1 or more digits. |max_digits|
// specifies the maximum number of digits to process. Returns true if a valid
// number is found, false otherwise.
static bool VerifyNumber(const uint8_t* buffer,
int buffer_size,
int* offset,
int max_digits) {
RCHECK(*offset < buffer_size);
// Skip over any leading space.
while (isspace(buffer[*offset])) {
++(*offset);
RCHECK(*offset < buffer_size);
}
// Need to process up to max_digits digits.
int numSeen = 0;
while (--max_digits >= 0 && isdigit(buffer[*offset])) {
++numSeen;
++(*offset);
if (*offset >= buffer_size)
return true; // Out of space but seen a digit.
}
// Success if at least one digit seen.
return (numSeen > 0);
}
// Check that the next character in |buffer| is one of |c1| or |c2|. |c2| is
// optional. Returns true if there is a match, false if no match or out of
// space.
static inline bool VerifyCharacters(const uint8_t* buffer,
int buffer_size,
int* offset,
char c1,
char c2) {
RCHECK(*offset < buffer_size);
char c = static_cast<char>(buffer[(*offset)++]);
return (c == c1 || (c == c2 && c2 != 0));
}
// Checks for a SRT container.
static bool CheckSrt(const uint8_t* buffer, int buffer_size) {
// Reference: http://en.wikipedia.org/wiki/SubRip
RCHECK(buffer_size > 20);
// First line should just be the subtitle sequence number.
int offset = StartsWith(buffer, buffer_size, UTF8_BYTE_ORDER_MARK) ? 3 : 0;
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 100));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, '\n', '\r'));
// Skip any additional \n\r.
while (VerifyCharacters(buffer, buffer_size, &offset, '\n', '\r')) {}
--offset; // Since VerifyCharacters() gobbled up the next non-CR/LF.
// Second line should look like the following:
// 00:00:10,500 --> 00:00:13,000
// Units separator can be , or .
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 100));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ':', 0));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 2));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ':', 0));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 2));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ',', '.'));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 3));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ' ', 0));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, '-', 0));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, '-', 0));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, '>', 0));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ' ', 0));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 100));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ':', 0));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 2));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ':', 0));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 2));
RCHECK(VerifyCharacters(buffer, buffer_size, &offset, ',', '.'));
RCHECK(VerifyNumber(buffer, buffer_size, &offset, 3));
return true;
}
// Read a Matroska Element Id.
static int GetElementId(BitReader* reader) {
// Element ID is coded with the leading zero bits (max 3) determining size.
// If it is an invalid encoding or the end of the buffer is reached,
// return -1 as a tag that won't be expected.
if (reader->bits_available() >= 8) {
int num_bits_to_read = 0;
static int prefix[] = { 0x80, 0x4000, 0x200000, 0x10000000 };
for (int i = 0; i < 4; ++i) {
num_bits_to_read += 7;
if (ReadBits(reader, 1) == 1) {
if (reader->bits_available() < num_bits_to_read)
break;
// prefix[] adds back the bits read individually.
return ReadBits(reader, num_bits_to_read) | prefix[i];
}
}
}
// Invalid encoding, return something not expected.
return -1;
}
// Read a Matroska Unsigned Integer (VINT).
static uint64_t GetVint(BitReader* reader) {
// Values are coded with the leading zero bits (max 7) determining size.
// If it is an invalid coding or the end of the buffer is reached,
// return something that will go off the end of the buffer.
if (reader->bits_available() >= 8) {
int num_bits_to_read = 0;
for (int i = 0; i < 8; ++i) {
num_bits_to_read += 7;
if (ReadBits(reader, 1) == 1) {
if (reader->bits_available() < num_bits_to_read)
break;
return ReadBits(reader, num_bits_to_read);
}
}
}
// Incorrect format (more than 7 leading 0's) or off the end of the buffer.
// Since the return value is used as a byte size, return a value that will
// cause a failure when used.
return (reader->bits_available() / 8) + 2;
}
// Additional checks for a WEBM container.
static bool CheckWebm(const uint8_t* buffer, int buffer_size) {
// Reference: http://www.matroska.org/technical/specs/index.html
RCHECK(buffer_size > 12);
BitReader reader(buffer, buffer_size);
// Verify starting Element Id.
RCHECK(GetElementId(&reader) == 0x1a45dfa3);
// Get the header size, and ensure there are enough bits to check.
int header_size = GetVint(&reader);
RCHECK(reader.bits_available() / 8 >= header_size);
// Loop through the header.
while (reader.bits_available() > 0) {
int tag = GetElementId(&reader);
int tagsize = GetVint(&reader);
switch (tag) {
case 0x4286: // EBMLVersion
case 0x42f7: // EBMLReadVersion
case 0x42f2: // EBMLMaxIdLength
case 0x42f3: // EBMLMaxSizeLength
case 0x4287: // DocTypeVersion
case 0x4285: // DocTypeReadVersion
case 0xec: // void
case 0xbf: // CRC32
RCHECK(reader.SkipBits(tagsize * 8));
break;
case 0x4282: // EBMLDocType
// Need to see "webm" or "matroska" next.
switch (ReadBits(&reader, 32)) {
case TAG('w', 'e', 'b', 'm') :
return true;
case TAG('m', 'a', 't', 'r') :
return (ReadBits(&reader, 32) == TAG('o', 's', 'k', 'a'));
}
return false;
default: // Unrecognized tag
return false;
}
}
return false;
}
enum VC1StartCodes {
VC1_FRAME_START_CODE = 0x0d,
VC1_ENTRY_POINT_START_CODE = 0x0e,
VC1_SEQUENCE_START_CODE = 0x0f
};
// Checks for a VC1 bitstream container.
static bool CheckVC1(const uint8_t* buffer, int buffer_size) {
// Reference: SMPTE 421M
// (http://standards.smpte.org/content/978-1-61482-555-5/st-421-2006/SEC1.body.pdf)
// However, no length ... simply scan for start code values.
// Expect to see SEQ | [ [ ENTRY ] PIC* ]*
// Note tags are very similar to H.264.
RCHECK(buffer_size >= 24);
// First check for Bitstream Metadata Serialization (Annex L)
if (buffer[0] == 0xc5 &&
Read32(buffer + 4) == 0x04 &&
Read32(buffer + 20) == 0x0c) {
// Verify settings in STRUCT_C and STRUCT_A
BitReader reader(buffer + 8, 12);
int profile = ReadBits(&reader, 4);
if (profile == 0 || profile == 4) { // simple or main
// Skip FRMRTQ_POSTPROC, BITRTQ_POSTPROC, and LOOPFILTER.
reader.SkipBits(3 + 5 + 1);
// Next bit must be 0.
RCHECK(ReadBits(&reader, 1) == 0);
// Skip MULTIRES.
reader.SkipBits(1);
// Next bit must be 1.
RCHECK(ReadBits(&reader, 1) == 1);
// Skip FASTUVMC, EXTENDED_MV, DQUANT, and VSTRANSFORM.
reader.SkipBits(1 + 1 + 2 + 1);
// Next bit must be 0.
RCHECK(ReadBits(&reader, 1) == 0);
// Skip OVERLAP, SYNCMARKER, RANGERED, MAXBFRAMES, QUANTIZER, and
// FINTERPFLAG.
reader.SkipBits(1 + 1 + 1 + 3 + 2 + 1);
// Next bit must be 1.
RCHECK(ReadBits(&reader, 1) == 1);
} else {
RCHECK(profile == 12); // Other profile values not allowed.
RCHECK(ReadBits(&reader, 28) == 0);
}
// Now check HORIZ_SIZE and VERT_SIZE, which must be 8192 or less.
RCHECK(ReadBits(&reader, 32) <= 8192);
RCHECK(ReadBits(&reader, 32) <= 8192);
return true;
}
// Buffer isn't Bitstream Metadata, so scan for start codes.
int offset = 0;
int sequence_start_code = 0;
int frame_start_code = 0;
while (true) {
// Advance to start_code, if there is one.
if (!AdvanceToStartCode(buffer, buffer_size, &offset, 5, 24, 1)) {
// Not a complete sequence in memory, so return true if we've seen a
// sequence start and a frame start (not checking entry points since
// they only occur in advanced profiles).
return (sequence_start_code > 0 && frame_start_code > 0);
}
// Now verify the block. AdvanceToStartCode() made sure that there are
// at least 5 bytes remaining in the buffer.
BitReader reader(buffer + offset, 5);
RCHECK(ReadBits(&reader, 24) == 1);
// Keep track of the number of certain types received.
switch (ReadBits(&reader, 8)) {
case VC1_SEQUENCE_START_CODE: {
++sequence_start_code;
switch (ReadBits(&reader, 2)) {
case 0: // simple
case 1: // main
RCHECK(ReadBits(&reader, 2) == 0);
break;
case 2: // complex
return false;
case 3: // advanced
RCHECK(ReadBits(&reader, 3) <= 4); // Verify level = 0..4
RCHECK(ReadBits(&reader, 2) == 1); // Verify colordiff_format = 1
break;
}
break;
}
case VC1_ENTRY_POINT_START_CODE:
// No fields in entry data to check. However, it must occur after
// sequence header.
RCHECK(sequence_start_code > 0);
break;
case VC1_FRAME_START_CODE:
++frame_start_code;
break;
}
offset += 5;
}
}
// For some formats the signature is a bunch of characters. They are defined
// below. Note that the first 4 characters of the string may be used as a TAG
// in LookupContainerByFirst4. For signatures that contain embedded \0, use
// uint8_t[].
static const char kAmrSignature[] = "#!AMR";
static const uint8_t kAsfSignature[] = {0x30, 0x26, 0xb2, 0x75, 0x8e, 0x66,
0xcf, 0x11, 0xa6, 0xd9, 0x00, 0xaa,
0x00, 0x62, 0xce, 0x6c};
static const char kAssSignature[] = "[Script Info]";
static const char kAssBomSignature[] = UTF8_BYTE_ORDER_MARK "[Script Info]";
static const uint8_t kWtvSignature[] = {0xb7, 0xd8, 0x00, 0x20, 0x37, 0x49,
0xda, 0x11, 0xa6, 0x4e, 0x00, 0x07,
0xe9, 0x5e, 0xad, 0x8d};
// Attempt to determine the container type from the buffer provided. This is
// a simple pass, that uses the first 4 bytes of the buffer as an index to get
// a rough idea of the container format.
static MediaContainerName LookupContainerByFirst4(const uint8_t* buffer,
int buffer_size) {
// Minimum size that the code expects to exist without checking size.
if (buffer_size < 12)
return CONTAINER_UNKNOWN;
uint32_t first4 = Read32(buffer);
switch (first4) {
case 0x1a45dfa3:
if (CheckWebm(buffer, buffer_size))
return CONTAINER_WEBM;
break;
case 0x3026b275:
if (StartsWith(buffer,
buffer_size,
kAsfSignature,
sizeof(kAsfSignature))) {
return CONTAINER_ASF;
}
break;
case TAG('#','!','A','M'):
if (StartsWith(buffer, buffer_size, kAmrSignature))
return CONTAINER_AMR;
break;
case TAG('#','E','X','T'):
if (CheckHls(buffer, buffer_size))
return CONTAINER_HLS;
break;
case TAG('.','R','M','F'):
if (buffer[4] == 0 && buffer[5] == 0)
return CONTAINER_RM;
break;
case TAG('.','r','a','\xfd'):
return CONTAINER_RM;
case TAG('B','I','K','b'):
case TAG('B','I','K','d'):
case TAG('B','I','K','f'):
case TAG('B','I','K','g'):
case TAG('B','I','K','h'):
case TAG('B','I','K','i'):
if (CheckBink(buffer, buffer_size))
return CONTAINER_BINK;
break;
case TAG('c','a','f','f'):
if (CheckCaf(buffer, buffer_size))
return CONTAINER_CAF;
break;
case TAG('D','E','X','A'):
if (buffer_size > 15 &&
Read16(buffer + 11) <= 2048 &&
Read16(buffer + 13) <= 2048) {
return CONTAINER_DXA;
}
break;
case TAG('D','T','S','H'):
if (Read32(buffer + 4) == TAG('D','H','D','R'))
return CONTAINER_DTSHD;
break;
case 0x64a30100:
case 0x64a30200:
case 0x64a30300:
case 0x64a30400:
case 0x0001a364:
case 0x0002a364:
case 0x0003a364:
if (Read32(buffer + 4) != 0 && Read32(buffer + 8) != 0)
return CONTAINER_IRCAM;
break;
case TAG('f','L','a','C'):
return CONTAINER_FLAC;
case TAG('F','L','V',0):
case TAG('F','L','V',1):
case TAG('F','L','V',2):
case TAG('F','L','V',3):
case TAG('F','L','V',4):
if (buffer[5] == 0 && Read32(buffer + 5) > 8)
return CONTAINER_FLV;
break;
case TAG('F','O','R','M'):
switch (Read32(buffer + 8)) {
case TAG('A','I','F','F'):
case TAG('A','I','F','C'):
return CONTAINER_AIFF;
}
break;
case TAG('M','A','C',' '):
return CONTAINER_APE;
case TAG('O','N','2',' '):
if (Read32(buffer + 8) == TAG('O','N','2','f'))
return CONTAINER_AVI;
break;
case TAG('O','g','g','S'):
if (buffer[5] <= 7)
return CONTAINER_OGG;
break;
case TAG('R','F','6','4'):
if (buffer_size > 16 && Read32(buffer + 12) == TAG('d','s','6','4'))
return CONTAINER_WAV;
break;
case TAG('R','I','F','F'):
switch (Read32(buffer + 8)) {
case TAG('A','V','I',' '):
case TAG('A','V','I','X'):
case TAG('A','V','I','\x19'):
case TAG('A','M','V',' '):
return CONTAINER_AVI;
case TAG('W','A','V','E'):
return CONTAINER_WAV;
}
break;
case TAG('[','S','c','r'):
if (StartsWith(buffer, buffer_size, kAssSignature))
return CONTAINER_ASS;
break;
case TAG('\xef','\xbb','\xbf','['):
if (StartsWith(buffer, buffer_size, kAssBomSignature))
return CONTAINER_ASS;
break;
case 0x7ffe8001:
case 0xfe7f0180:
case 0x1fffe800:
case 0xff1f00e8:
if (CheckDts(buffer, buffer_size))
return CONTAINER_DTS;
break;
case 0xb7d80020:
if (StartsWith(buffer,
buffer_size,
kWtvSignature,
sizeof(kWtvSignature))) {
return CONTAINER_WTV;
}
break;
case 0x000001ba:
return CONTAINER_MPEG2PS;
}
// Now try a few different ones that look at something other
// than the first 4 bytes.
uint32_t first3 = first4 & 0xffffff00;
switch (first3) {
case TAG('C','W','S',0):
case TAG('F','W','S',0):
return CONTAINER_SWF;
case TAG('I','D','3',0):
if (CheckMp3(buffer, buffer_size, true))
return CONTAINER_MP3;
break;
}
// Maybe the first 2 characters are something we can use.
uint32_t first2 = Read16(buffer);
switch (first2) {
case kAc3SyncWord:
if (CheckAc3(buffer, buffer_size))
return CONTAINER_AC3;
if (CheckEac3(buffer, buffer_size))
return CONTAINER_EAC3;
break;
case 0xfff0:
case 0xfff1:
case 0xfff8:
case 0xfff9:
if (CheckAac(buffer, buffer_size))
return CONTAINER_AAC;
break;
}
// Check if the file is in MP3 format without the header.
if (CheckMp3(buffer, buffer_size, false))
return CONTAINER_MP3;
return CONTAINER_UNKNOWN;
}
namespace {
const char kWebVtt[] = "WEBVTT";
bool CheckWebVtt(const uint8_t* buffer, int buffer_size) {
const int offset =
StartsWith(buffer, buffer_size, UTF8_BYTE_ORDER_MARK) ? 3 : 0;
return StartsWith(buffer + offset, buffer_size - offset,
reinterpret_cast<const uint8_t*>(kWebVtt),
arraysize(kWebVtt) - 1);
}
bool CheckTtml(const uint8_t* buffer, int buffer_size) {
// Sanity check first before reading the entire thing.
if (!StartsWith(buffer, buffer_size, "<?xml"))
return false;
// Make sure that it can be parsed so that it doesn't error later in the
// process. Not doing a schema check to allow TTMLs that makes some sense but
// not necessarily compliant to the schema.
xml::scoped_xml_ptr<xmlDoc> doc(
xmlParseMemory(reinterpret_cast<const char*>(buffer), buffer_size));
if (!doc)
return false;
xmlNodePtr root_node = xmlDocGetRootElement(doc.get());
std::string root_node_name(reinterpret_cast<const char*>(root_node->name));
// "tt" is supposed to be the top level element for ttml.
return root_node_name == "tt";
}
} // namespace
// Attempt to determine the container name from the buffer provided.
MediaContainerName DetermineContainer(const uint8_t* buffer, int buffer_size) {
DCHECK(buffer);
// Since MOV/QuickTime/MPEG4 streams are common, check for them first.
if (CheckMov(buffer, buffer_size))
return CONTAINER_MOV;
// Next attempt the simple checks, that typically look at just the
// first few bytes of the file.
MediaContainerName result = LookupContainerByFirst4(buffer, buffer_size);
if (result != CONTAINER_UNKNOWN)
return result;
// WebVTT check only checks for the first few bytes.
if (CheckWebVtt(buffer, buffer_size))
return CONTAINER_WEBVTT;
// Additional checks that may scan a portion of the buffer.
if (CheckMpeg2ProgramStream(buffer, buffer_size))
return CONTAINER_MPEG2PS;
if (CheckMpeg2TransportStream(buffer, buffer_size))
return CONTAINER_MPEG2TS;
if (CheckMJpeg(buffer, buffer_size))
return CONTAINER_MJPEG;
if (CheckDV(buffer, buffer_size))
return CONTAINER_DV;
if (CheckH261(buffer, buffer_size))
return CONTAINER_H261;
if (CheckH263(buffer, buffer_size))
return CONTAINER_H263;
if (CheckH264(buffer, buffer_size))
return CONTAINER_H264;
if (CheckMpeg4BitStream(buffer, buffer_size))
return CONTAINER_MPEG4BS;
if (CheckVC1(buffer, buffer_size))
return CONTAINER_VC1;
if (CheckSrt(buffer, buffer_size))
return CONTAINER_SRT;
if (CheckGsm(buffer, buffer_size))
return CONTAINER_GSM;
// AC3/EAC3 might not start at the beginning of the stream,
// so scan for a start code.
int offset = 1; // No need to start at byte 0 due to First4 check.
if (AdvanceToStartCode(buffer, buffer_size, &offset, 4, 16, kAc3SyncWord)) {
if (CheckAc3(buffer + offset, buffer_size - offset))
return CONTAINER_AC3;
if (CheckEac3(buffer + offset, buffer_size - offset))
return CONTAINER_EAC3;
}
// To do a TTML check, it parses the XML which requires scanning
// the whole content.
if (CheckTtml(buffer, buffer_size))
return CONTAINER_TTML;
return CONTAINER_UNKNOWN;
}
} // namespace media
} // namespace edash_packager
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