Why AVCodecContext extradata is NULL?

Question

I am trying to decode h264 video using ffmpeg and stagefright library. I'm using this example.

The example shows how to decode mp4 files, but i want to decode only h264 video.

Here is piece of my code..

    AVFormatSource::AVFormatSource(const char *videoPath) 
    {
        av_register_all();

        mDataSource = avformat_alloc_context();
        avformat_open_input(&mDataSource, videoPath, NULL, NULL);
        for (int i = 0; i < mDataSource->nb_streams; i++) 
        {
            if (mDataSource->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) 
            {
                mVideoIndex = i;
                break;
            }
        }
        mVideoTrack = mDataSource->streams[mVideoIndex]->codec;

        size_t bufferSize = (mVideoTrack->width * mVideoTrack->height * 3) / 2;
        mGroup.add_buffer(new MediaBuffer(bufferSize));
        mFormat = new MetaData;

        switch (mVideoTrack->codec_id == CODEC_ID_H264) 
        {
            mConverter = av_bitstream_filter_init("h264_mp4toannexb");
            mFormat->setCString(kKeyMIMEType, MEDIA_MIMETYPE_VIDEO_AVC);
            if (mVideoTrack->extradata[0] == 1) //SIGSEGV Here
            {
                mFormat->setCString(kKeyMIMEType, MEDIA_MIMETYPE_VIDEO_AVC);
                mFormat->setData(kKeyAVCC, kTypeAVCC, mVideoTrack->extradata,
                                 mVideoTrack->extradata_size);
            }
         }

        mFormat->setInt32(kKeyWidth, mVideoTrack->width);
        mFormat->setInt32(kKeyHeight, mVideoTrack->height);
    }

mVideoTrack->extradata is NULL. What i'm doing wrong?? My question is, what should be in mVideoTrack->extradata for kKeyAVCC ??

Please help me, I need Your help. Thanks in advance.

Greenfinch

You may find all required information here aviadr1.blogspot.com/2010/05/… – Dissolution

Answer 1

If your input is a raw h.264 file, It is already in annex B format. So you do not need to do the "h264_mp4toannexb" conversion. In addition, in annex B, the SPS/PPS are sent inline with the first (or every) IDR frame. So no extra data is needed. Read more here: Possible Locations for Sequence/Picture Parameter Set(s) for H.264 Stream

Defazio

Thanks very much for your reply. As i understood, in this header of h264.. 00 00 00 01 67 64 00 1f ac d9 40 50 04 5f 9a 10 00 00 3e 90 00 0b b8 08 f1 83 19 60 00 00 00 01 68 eb ec b2 2c. This data is SPS and PPS. So... I don't need this code mFormat->setData(kKeyAVCC, kTypeAVCC, mVideoTrack->extradata, mVideoTrack->extradata_size);. Am i right? – Greenfinch

Correct, and you don't need the bitstream filter. – Defazio