Add support for skip_encryption stream descriptor (#219)

This option makes it possible to control encryption for specific streams,
e.g. for audio and video separately.

packager/app/packager_main.cc

@@ -107,7 +107,9 @@ const char kUsage[] =
     "    The group ID for the output stream. For HLS this is used as the\n"
     "    GROUP-ID attribute for EXT-X-MEDIA.\n"
     "  - playlist_name: Required for HLS output.\n"
-    "    Name of the playlist for the stream. Usually ends with '.m3u8'.\n";
+    "    Name of the playlist for the stream. Usually ends with '.m3u8'.\n"
+    "  - skip_encryption=0|1: Optional. Defaults to 0 if not specified. If\n"
+    "    it is set to 1, no encryption of the stream will be made.\n";
 
 const char kMediaInfoSuffix[] = ".media_info";
 
@@ -378,7 +380,7 @@ bool CreateRemuxJobs(const StreamDescriptorList& stream_descriptors,
     handlers.push_back(chunking_handler);
 
     Status status;
-    if (encryption_key_source) {
+    if (encryption_key_source && !stream_iter->skip_encryption) {
       auto new_encryption_options = encryption_options;
       // Use Sample AES in MPEG2TS.
       // TODO(kqyang): Consider adding a new flag to enable Sample AES as we

packager/app/stream_descriptor.cc

@@ -31,6 +31,7 @@ enum FieldType {
   kHlsGroupIdField,
   kHlsPlaylistNameField,
   kTrickPlayFactorField,
+  kSkipEncryptionField,
 };
 
 struct FieldNameToTypeMapping {
@@ -60,6 +61,7 @@ const FieldNameToTypeMapping kFieldNameTypeMappings[] = {
     {"playlist_name", kHlsPlaylistNameField},
     {"trick_play_factor", kTrickPlayFactorField},
     {"tpf", kTrickPlayFactorField},
+    {"skip_encryption", kSkipEncryptionField},
 };
 
 FieldType GetFieldType(const std::string& field_name) {
@@ -158,6 +160,21 @@ bool InsertStreamDescriptor(const std::string& descriptor_string,
         descriptor.trick_play_factor = factor;
         break;
       }
+      case kSkipEncryptionField: {
+        unsigned skip_encryption_value;
+        if (!base::StringToUint(iter->second, &skip_encryption_value)) {
+          LOG(ERROR) << "Non-numeric option for skip encryption field "
+                        "specified (" << iter->second << ").";
+          return false;
+        }
+        if (skip_encryption_value > 1) {
+          LOG(ERROR) << "skip_encryption should be either 0 or 1.";
+          return false;
+        }
+
+        descriptor.skip_encryption = skip_encryption_value > 0;
+        break;
+      }
       default:
         LOG(ERROR) << "Unknown field in stream descriptor (\"" << iter->first
                    << "\").";

packager/app/stream_descriptor.h

@@ -34,6 +34,7 @@ struct StreamDescriptor {
   std::string hls_group_id;
   std::string hls_playlist_name;
   uint32_t trick_play_factor = 0;
+  bool skip_encryption = false;
 };
 
 class StreamDescriptorCompareFn {

packager/app/test/packager_test.py

@@ -240,6 +240,15 @@ class PackagerAppTest(unittest.TestCase):
     self._VerifyDecryption(self.output[0], 'bear-640x360-a-golden.mp4')
     self._VerifyDecryption(self.output[1], 'bear-640x360-v-golden.mp4')
 
+  def testPackageWithEncryptionOfOnlyVideoStream(self):
+    self.packager.Package(
+        self._GetStreams(['audio,skip_encryption=1', 'video']),
+        self._GetFlags(encryption=True))
+    self._DiffGold(self.output[0], 'bear-640x360-a-golden.mp4')
+    self._DiffGold(self.output[1], 'bear-640x360-v-cenc-golden.mp4')
+    self._DiffGold(self.mpd_output, 'bear-640x360-a-clear-v-cenc-golden.mpd')
+    self._VerifyDecryption(self.output[1], 'bear-640x360-v-golden.mp4')
+
   def testPackageWithEncryptionAndTrickPlay(self):
     self.packager.Package(
         self._GetStreams(['audio', 'video', 'video,trick_play_factor=1']),

packager/app/test/testdata/bear-640x360-a-clear-v-cenc-golden.mpd

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--Generated with https://github.com/google/shaka-packager version <tag>-<hash>-<test>-->
+<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xsi:schemaLocation="urn:mpeg:dash:schema:mpd:2011 DASH-MPD.xsd" xmlns:cenc="urn:mpeg:cenc:2013" profiles="urn:mpeg:dash:profile:isoff-on-demand:2011" minBufferTime="PT2S" type="static" mediaPresentationDuration="PT2.76317S">
+  <Period id="0">
+    <AdaptationSet id="0" contentType="video" width="640" height="360" frameRate="30000/1001" subsegmentAlignment="true" par="16:9">
+      <ContentProtection value="cenc" schemeIdUri="urn:mpeg:dash:mp4protection:2011" cenc:default_KID="31323334-3536-3738-3930-313233343536"/>
+      <ContentProtection schemeIdUri="urn:uuid:1077efec-c0b2-4d02-ace3-3c1e52e2fb4b">
+        <cenc:pssh>AAAANHBzc2gBAAAAEHfv7MCyTQKs4zweUuL7SwAAAAExMjM0NTY3ODkwMTIzNDU2AAAAAA==</cenc:pssh>
+      </ContentProtection>
+      <Representation id="0" bandwidth="885590" codecs="avc1.64001e" mimeType="video/mp4" sar="1:1">
+        <BaseURL>output_video.mp4</BaseURL>
+        <SegmentBase indexRange="1091-1158" timescale="30000">
+          <Initialization range="0-1090"/>
+        </SegmentBase>
+      </Representation>
+    </AdaptationSet>
+    <AdaptationSet id="1" contentType="audio" subsegmentAlignment="true">
+      <Representation id="1" bandwidth="126510" codecs="mp4a.40.2" mimeType="audio/mp4" audioSamplingRate="44100">
+        <AudioChannelConfiguration schemeIdUri="urn:mpeg:dash:23003:3:audio_channel_configuration:2011" value="2"/>
+        <BaseURL>output_audio_skip_encryption_1.mp4</BaseURL>
+        <SegmentBase indexRange="757-824" timescale="44100">
+          <Initialization range="0-756"/>
+        </SegmentBase>
+      </Representation>
+    </AdaptationSet>
+  </Period>
+</MPD>