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• h264 ffmpeg : How to initialize ffmpeg to decode NALs created with x264

  19 février 2024, par Raul Calvo

  I encoded some frames using x264, using x264_encoder_encode() and after that I created AVPackets using a function like this :

  


  bool PacketizeNals( uint8_t* a_pNalBuffer, int a_nNalBufferSize, AVPacket* a_pPacket )
{
    if ( !a_pPacket )
return false;
    a_pPacket->data = a_pNalBuffer;
    a_pPacket->size = a_nNalBufferSize;
    a_pPacket->stream_index = 0;
    a_pPacket->flags = AV_PKT_FLAG_KEY;

    a_pPacket->pts = int64_t(0x8000000000000000);
    a_pPacket->dts = int64_t(0x8000000000000000);
}


  


  I call this function like this :

  


  x264_nal_t* nals;
int num_nals = encode_frame(pic, &nals);
for (int i = 0; i < num_nals; i++)
{
    AVPacket* pPacket = ( AVPacket* )av_malloc( sizeof( AVPacket ) );
    av_init_packet( pPacket );
    if ( PacketizeNals( nals[i].p_payload, nals[i].i_payload, pPacket ) )
    {
        packets.push_back( pPacket );
    }
}


  


  Now what I want to do is to decode these AVPackets using avcodec_decode_video2. I think the problem is that I haven't properly initialized the decoder because to encode I used "ultrafast" profile and "zerolatency" tune (x264) and to decode I don't know how to specify these options to ffmpeg.

  


  In some examples I have read people initialize the decoder using the file where the video is stored, but in this case I have the AVPackets directly.

  


  What I'm doing to try to decode is :

  


  avcodec_init();  
avcodec_register_all();  
AVCodec* pCodec;  
pCodec=avcodec_find_decoder(CODEC_ID_H264);  
AVCodecContext* pCodecContext;  
pCodecContext=avcodec_alloc_context();  
avcodec_open(pCodecContext,pCodec);  
pCodecContext->width = 320;
pCodecContext->height = 200;
pCodecContext->extradata = NULL;
unsigned int nNumPackets = packets.size();
int frameFinished = 0;
for ( auto it = packets.begin(); it != packets.end(); it++ )
{
    AVFrame* pFrame;
    pFrame = avcodec_alloc_frame();
    AVPacket* pPacket = *it;
    int iReturn = avcodec_decode_video2( pCodecContext, pFrame, &frameFinished, pPacket );
}


  


  But iReturn is always -1.

  


  Can anyone help me ? Sorry if my knowledge in this area is low, I'm new.

  


• h264 ffmpeg : How to initialize ffmpeg to decode NALs created with x264

  19 février 2024, par Raul Calvo

  I encoded some frames using x264, using x264_encoder_encode() and after that I created AVPackets using a function like this :

  


  bool PacketizeNals( uint8_t* a_pNalBuffer, int a_nNalBufferSize, AVPacket* a_pPacket )
{
    if ( !a_pPacket )
return false;
    a_pPacket->data = a_pNalBuffer;
    a_pPacket->size = a_nNalBufferSize;
    a_pPacket->stream_index = 0;
    a_pPacket->flags = AV_PKT_FLAG_KEY;

    a_pPacket->pts = int64_t(0x8000000000000000);
    a_pPacket->dts = int64_t(0x8000000000000000);
}


  


  I call this function like this :

  


  x264_nal_t* nals;
int num_nals = encode_frame(pic, &nals);
for (int i = 0; i < num_nals; i++)
{
    AVPacket* pPacket = ( AVPacket* )av_malloc( sizeof( AVPacket ) );
    av_init_packet( pPacket );
    if ( PacketizeNals( nals[i].p_payload, nals[i].i_payload, pPacket ) )
    {
        packets.push_back( pPacket );
    }
}


  


  Now what I want to do is to decode these AVPackets using avcodec_decode_video2. I think the problem is that I haven't properly initialized the decoder because to encode I used "ultrafast" profile and "zerolatency" tune (x264) and to decode I don't know how to specify these options to ffmpeg.

  


  In some examples I have read people initialize the decoder using the file where the video is stored, but in this case I have the AVPackets directly.

  


  What I'm doing to try to decode is :

  


  avcodec_init();  
avcodec_register_all();  
AVCodec* pCodec;  
pCodec=avcodec_find_decoder(CODEC_ID_H264);  
AVCodecContext* pCodecContext;  
pCodecContext=avcodec_alloc_context();  
avcodec_open(pCodecContext,pCodec);  
pCodecContext->width = 320;
pCodecContext->height = 200;
pCodecContext->extradata = NULL;
unsigned int nNumPackets = packets.size();
int frameFinished = 0;
for ( auto it = packets.begin(); it != packets.end(); it++ )
{
    AVFrame* pFrame;
    pFrame = avcodec_alloc_frame();
    AVPacket* pPacket = *it;
    int iReturn = avcodec_decode_video2( pCodecContext, pFrame, &frameFinished, pPacket );
}


  


  But iReturn is always -1.

  


  Can anyone help me ? Sorry if my knowledge in this area is low, I'm new.

  


• x86 : Remove inline MMX assembly that clobbers the FPU state

  26 janvier 2024, par Martin Storsjö

  x86 : Remove inline MMX assembly that clobbers the FPU state
  These inline implementations of AV_COPY64, AV_SWAP64 and AV_ZERO64
  
  are known to clobber the FPU state - which has to be restored
  
  with the 'emms' instruction afterwards.
  This was known and signaled with the FF_COPY_SWAP_ZERO_USES_MMX
  
  define, which calling code seems to have been supposed to check,
  
  in order to call emms_c() after using them. See
  
  0b1972d4096df5879038f0af776f87f41e90ebd4,
  
  29c4c0886d143790fcbeddbe40a23dfc6f56345c and
  
  df215e575850e41b19aeb1fd99e53372a6b3d537 for history on earlier
  
  fixes in the same area.
  However, new code can use these AV_*64() macros without knowing
  
  about the need to call emms_c().
  Just get rid of these dangerous inline assembly snippets ; this
  
  doesn't make any difference for 64 bit architectures anyway.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavcodec/dca_core.c
  • [DH] libavutil/x86/intreadwrite.h