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POh264 ffmpeg: How to initialize ffmpeg to decode NALs created with x264
 

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  1. POh264 ffmpeg: How to initialize ffmpeg to decode NALs created with x264
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    <p>I have encoded some frames using x264, using x264_encoder_encode and after that I have created AVPackets using a function like this:</p> <pre><code>bool PacketizeNals( uint8_t* a_pNalBuffer, int a_nNalBufferSize, AVPacket* a_pPacket ) { if ( !a_pPacket ) return false; a_pPacket-&gt;data = a_pNalBuffer; a_pPacket-&gt;size = a_nNalBufferSize; a_pPacket-&gt;stream_index = 0; a_pPacket-&gt;flags = AV_PKT_FLAG_KEY; a_pPacket-&gt;pts = int64_t(0x8000000000000000); a_pPacket-&gt;dts = int64_t(0x8000000000000000); } </code></pre> <p>I call this function like this:</p> <pre><code>x264_nal_t* nals; int num_nals = encode_frame(pic, &amp;nals); for (int i = 0; i &lt; 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 ); } } </code></pre> <p>Now what I want to do is to decode these AVPackets using avcodec_decode_video2. I think the problem is that I haven't initialized properly the decoder because to encode I used "ultrafast" profile and "zerolatency" tune ( x264 ) and to decode I don't know how to specify to ffmpeg these options. In some examples I have read people initialize the decoder using the file where the video is stored, but in this case I have directly the AVPackets. What I'm doing to try to decode is:</p> <pre><code>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-&gt;width = 320; pCodecContext-&gt;height = 200; pCodecContext-&gt;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, &amp;frameFinished, pPacket ); } </code></pre> <p>But in iReturn always is -1.</p> <p>Can anyone help me? Sorry if my knowledge in this area es low, I'm new.</p> <p>Thanks.</p>
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