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POFast way of opening Live Input with libavcodec
 

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  1. POFast way of opening Live Input with libavcodec
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    <p>I'm currently working with a live video input from the Hauppauge WinTV950Q, which gives me a live Video Input. </p> <p>I'm using the <code>libav*</code> and <code>Qt</code> library and am programming in <code>C/C++</code> on Linux. I use the recommended <code>avcodec_open_input()</code> for opening and processing (transcoding) the input for the use on mobile Devices. I want to be able to watch TV on my mobile Devices and also be able to switch channels remotely. Everything works fine so far.</p> <p>My only problem is that the opening of an input takes between 5 and 20 seconds. Which is to slow for my use case, I would be okay with delays between 1-3 seconds. The v4l2-API which I formerly used for first tests actually manages to get switch times between 1-3seconds, I can not use it though because I need to do some transcoding so I can use the video data on my mobile devices.</p> <p><strong>Is there a way to improve the opening time of the <code>avformat_open_input()</code> call? Maybe some global variables in the library that need to be set before opening the input?</strong></p> <h2>Here's the relevant piece of code:</h2> <pre><code>const char* filename = "/dev/dvb/adapter0/dvr0"; int main(void) { /*Qt-Variables*/ QTime timer; /*General AV-IO*/ int i, videoStream, audioStream, frameFinished; AVFormatContext *ptrFormatContext; AVPacket ptrPacket; /*Audio related*/ AVCodecContext *aCodecCtx; AVCodecContext *aTargetCodecCtxt; AVCodec *aCodec; AVCodec *aTargetCodec; uint8_t *audio_samples; int frame_size_ptr; // AVSampleFormat ptrSampleFormats[2] = {AV_SAMPLE_FMT_S16, AV_SAMPLE_FMT_S32}; /*Video related*/ AVCodecContext *ptrCodecCtxt; AVCodecContext *vTargetCodecCtxt; AVCodec *ptrCodec; AVCodec *vTargetCodec; AVFrame *ptrFrame; /*Default Initialization of Variables*/ audioStream = videoStream = -1; audio_samples = NULL; /*Registering and initialization of the libav* codecs, formats, filter etc.*/ qDebug("Registering Codecs, Filter, Formats, Media Libraries etc..."); timer.start(); av_register_all(); avcodec_register_all(); qDebug()&lt;&lt;"Elapsed(ms): "&lt;&lt;timer.elapsed(); /*Assigning a memory array to the Format Context and the Frame for the Video decoding, now we can start working*/ qDebug("Allocating Codec Context and Frames for main Input..."); timer.start(); ptrFrame = avcodec_alloc_frame(); ptrFormatContext = avformat_alloc_context(); qDebug()&lt;&lt;"Elapsed(ms): "&lt;&lt;timer.elapsed(); /*Opening the Live Video Input, sometimes very slow.*/ qDebug("Trying to open the Input..."); timer.start(); if(avformat_open_input(&amp;ptrFormatContext, filename, NULL, NULL) != 0 ) { qDebug("Error opening the input"); exit(-1); } else qDebug()&lt;&lt;"Elapsed(ms): "&lt;&lt;timer.elapsed(); </code></pre> <h2>Here's the output:</h2> <pre><code>Registering Codecs, Filter, Formats, Media Libraries etc... Elapsed(ms): 0 Allocating Codec Context and Frames for main Input... Elapsed(ms): 0 Trying to open the Input... Elapsed(ms): 14752 </code></pre>
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    1. COhi mmoment, are you still working on this? I working on something similar; almost ready!
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