FFmpeg4/libavformat/rtpdec_mpa_robust.c

/*
 * RTP parser for loss tolerant payload format for MP3 audio (RFC 5219)
 * Copyright (c) 2015 Gilles Chanteperdrix <gch@xenomai.org>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/attributes.h"
#include "libavutil/intreadwrite.h"

#include "avio_internal.h"
#include "rtpdec_formats.h"

struct PayloadContext {
    unsigned adu_size;
    unsigned cur_size;
    uint32_t timestamp;
    uint8_t *split_buf;
    int split_pos, split_buf_size, split_pkts;
    AVIOContext *fragment;
};

static void mpa_robust_close_context(PayloadContext *data)
{
    ffio_free_dyn_buf(&data->fragment);
    av_free(data->split_buf);
}

static int mpa_robust_parse_rtp_header(AVFormatContext *ctx,
                                       const uint8_t *buf, int len,
                                       unsigned *adu_size, unsigned *cont)
{
    unsigned header_size;

    if (len < 2) {
        av_log(ctx, AV_LOG_ERROR, "Invalid %d bytes packet\n", len);
        return AVERROR_INVALIDDATA;
    }

    *cont = !!(buf[0] & 0x80);
    if (!(buf[0] & 0x40)) {
        header_size = 1;
        *adu_size = buf[0] & ~0xc0;
    } else {
        header_size = 2;
        *adu_size = AV_RB16(buf) & ~0xc000;
    }

    return header_size;
}

static int mpa_robust_parse_packet(AVFormatContext *ctx, PayloadContext *data,
                                   AVStream *st, AVPacket *pkt,
                                   uint32_t *timestamp, const uint8_t *buf,
                                   int len, uint16_t seq, int flags)
{
    unsigned adu_size, continuation;
    int err, header_size;

    if (!buf) {
        buf = &data->split_buf[data->split_pos];
        len = data->split_buf_size - data->split_pos;

        header_size = mpa_robust_parse_rtp_header(ctx, buf, len, &adu_size,
                                                  &continuation);
        if (header_size < 0) {
            av_freep(&data->split_buf);
            return header_size;
        }
        buf += header_size;
        len -= header_size;

        if (continuation || adu_size > len) {
            av_freep(&data->split_buf);
            av_log(ctx, AV_LOG_ERROR, "Invalid frame\n");
            return AVERROR_INVALIDDATA;
        }

        if ((err = av_new_packet(pkt, adu_size)) < 0) {
            av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
            return err;
        }

        pkt->stream_index = st->index;
        memcpy(pkt->data, buf, adu_size);

        data->split_pos += header_size + adu_size;

        if (data->split_pos == data->split_buf_size) {
            av_freep(&data->split_buf);
            return 0;
        }

        return 1;
    }


    header_size = mpa_robust_parse_rtp_header(ctx, buf, len, &adu_size,
                                              &continuation);
    if (header_size < 0)
        return header_size;

    buf += header_size;
    len -= header_size;

    if (!continuation && adu_size <= len) {
        /* One or more complete frames */

        if ((err = av_new_packet(pkt, adu_size)) < 0) {
            av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
            return err;
        }

        pkt->stream_index = st->index;
        memcpy(pkt->data, buf, adu_size);

        buf += adu_size;
        len -= adu_size;
        if (len) {
            data->split_buf_size = len;
            data->split_buf = av_malloc(data->split_buf_size);
            data->split_pos = 0;
            if (!data->split_buf) {
                av_log(ctx, AV_LOG_ERROR, "Out of memory.\n");
                av_packet_unref(pkt);
                return AVERROR(ENOMEM);
            }
            memcpy(data->split_buf, buf, data->split_buf_size);
            return 1;
        }
        return 0;
    } else if (!continuation) { /* && adu_size > len */
        /* First fragment */
        ffio_free_dyn_buf(&data->fragment);

        data->adu_size = adu_size;
        data->cur_size = len;
        data->timestamp = *timestamp;

        err = avio_open_dyn_buf(&data->fragment);
        if (err < 0)
            return err;

        avio_write(data->fragment, buf, len);
        return AVERROR(EAGAIN);
    }
    /* else continuation == 1 */

    /* Fragment other than first */
    if (!data->fragment) {
        av_log(ctx, AV_LOG_WARNING,
            "Received packet without a start fragment; dropping.\n");
        return AVERROR(EAGAIN);
    }
    if (adu_size != data->adu_size ||
        data->timestamp != *timestamp) {
        ffio_free_dyn_buf(&data->fragment);
        av_log(ctx, AV_LOG_ERROR, "Invalid packet received\n");
        return AVERROR_INVALIDDATA;
    }

    avio_write(data->fragment, buf, len);
    data->cur_size += len;

    if (data->cur_size < data->adu_size)
        return AVERROR(EAGAIN);

    err = ff_rtp_finalize_packet(pkt, &data->fragment, st->index);
    if (err < 0) {
        av_log(ctx, AV_LOG_ERROR,
               "Error occurred when getting fragment buffer.\n");
        return err;
    }

    return 0;
}

const RTPDynamicProtocolHandler ff_mpeg_audio_robust_dynamic_handler = {
    .enc_name          = "mpa-robust",
    .codec_type        = AVMEDIA_TYPE_AUDIO,
    .codec_id          = AV_CODEC_ID_MP3ADU,
    .need_parsing      = AVSTREAM_PARSE_HEADERS,
    .priv_data_size    = sizeof(PayloadContext),
    .close             = mpa_robust_close_context,
    .parse_packet      = mpa_robust_parse_packet,
};