[Libav-user] Very slow H264 stream decoding

[Bakhtiyarov Dmitriy]

Ok, I fix this delay.

I change settings of encoder and set:

m_params->i_keyint_max = 5;    //At this interval of frames force setted
IDR frame
m_params->b_intra_refresh = 0;  //use IDR frames instead periodic intra
refresh

Now it work correctly. Thanks for all.


2013/10/4 Дмитрий Бахтияров <bakhtiyarov.dima at gmail.com>

> Hi, all!
>
> I'm developing network application, which can play H264 video from RTSP
> stream. I use live555 for RTSP/RTP processing, libx264 for encoding and
> ffmpeg for decoding.
> My problem is in the decoder working - I have video stream with 12-15 fps,
> but avcodec_decode_video2 set got_image into not-null value very rarely -
> average 1 time per second or less. In a GUI its looks like very long
> freezes of interface, when one frame drawing on widgets few seconds.
>  When I connect to server using vlc all work correct - I have video with
> 12-15 fps.
>
> I have a such code for decoding:
>
> AVCodec* m_decoder;
> AVCodecContext* m_decoderContext;
> AVFrame* m_picture;
> AVPacket m_packet;
>
> //initialisation of decoder
> {
>     avcodec_register_all();
>     av_init_packet(&m_packet);
>     m_decoder = avcodec_find_decoder(CODEC_ID_H264);
>     if (!m_decoder)
>     {
>         QString str = QString("Can't find H264 decoder!");
>         emit criticalError(str);
>     }
>     m_decoderContext = avcodec_alloc_context3(m_decoder);
>
>     m_decoderContext->flags |= CODEC_FLAG_TRUNCATED;
>
>     m_decoderContext->flags |= CODEC_FLAG_LOW_DELAY;
>     //we can receive truncated frames
>     m_decoderContext->flags2 |= CODEC_FLAG2_CHUNKS;
>
>     AVDictionary* dictionary = nullptr;
>     if (avcodec_open2(m_decoderContext, m_decoder, &dictionary) < 0)
>     {
>         QString str = QString("Failed to open decoder!");
>         emit criticalError(str);
>     }
>     qDebug() << "H264 Decoder successfully opened";
>     m_picture = avcodec_alloc_frame();
> }
>
>
>
> //decoding frame; Frame_t is equal to vector<unsigned char>
> {
>     Frame_t enc_frame;
>     orig_frame >> enc_frame;
>     m_packet.size = enc_frame.size();
>     m_packet.data = enc_frame.data();
>
>     qDebug() << "H264Decoder: received encoded frame with framesize " <<
> enc_frame.size();
>
>     while(m_packet.size > 0)
>     {
>         int got_picture;
>         int len = avcodec_decode_video2(m_decoderContext, m_picture,
> &got_picture, &m_packet);
>         if (len < 0)
>         {
>             QString err("Decoding error");
>             qDebug() << err;
>             return false;
>         }
>         if (got_picture)
>         {
>             qDebug() << "H264Decoder: frame decoded!";
>             //.......
>         }
>     }
> }
>
> On the server side I have this encoder settings:
> {
>     m_params = new x264_param_t;
>     if (x264_param_default_preset(m_params, "ultrafast", "zerolatency") !=
> 0)
>         qDebug() << "presetting default values for x264 parameters
> failed!";
>
>     m_params->i_width = m_out_width;
>     m_params->i_height = m_out_height;
>     m_params->i_threads = 2;
>     m_params->i_fps_num = m_fps;  //avg 12-15
>     m_params->i_fps_den = 1;
>
>     m_params->i_keyint_max = 24;
>     m_params->b_intra_refresh = 1;
>
>     m_params->rc.i_rc_method = X264_RC_CRF;
>     m_params->rc.f_rf_constant = 25;
>     m_params->rc.f_rf_constant_max = 35;
>
>     m_params->b_repeat_headers = 1;
>     m_params->b_annexb = 1;
>     x264_param_apply_profile(m_params, "baseline");
>
>     m_encoder = x264_encoder_open(m_params);
>     if (m_encoder == nullptr)
>     {
>         qDebug() << "x264: encoder opening failed!";
>         abort();
>     }
>     m_in_pic = new x264_picture_t;
>
>     if (x264_picture_alloc( m_in_pic, X264_CSP_I420, 640, 480 ) != 0)
>         qDebug() << "x264: Picture allocating failed!";
>
>     x264_encoder_parameters(m_encoder, m_params);
>
>     m_out_pic = new x264_picture_t;
>
>     x264_nal_t* headers;
>     int pi_nal;
>     if (x264_encoder_headers(m_encoder, &headers, &pi_nal) < 0)
>         qDebug() << "Error creating NAL headers!";
> }
>
>
> What is the reason of this delay and how I can fix it?
>
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