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• what FFMPEG performance settings to use for processing videos for the web

  21 mai 2020, par eAbi

  I have a few questions regarding usage of ffmpeg for processing videos for the web. I'm a beginner so please bear with me (although I read some docs on the internet)

  



  Performance

  



  

  • First of all, given the fact that FFMPEG utilizes all cores at 100%, what is the actual parallelism efficiency ?

  


  



  Let's assume the following scenario. I have a video (fullHD, doesn't matter what encoders / compression format was used to obtain the video) and I want to resize (downscale) to various sizes (e.g. 240px, 480px and 720px height) using mp4 format (thus using libx264 with aac codecs).

  



  Using ffmpeg, I see that all of my laptop's cores (8) are used at 100% and I was wondering what scenarios can improve the overall performance of the whole processing task. So this leads us to basically 2 scenarios : Assuming the video mentioned above as input, for obtaining the 3 output videos (@ 240px, 480px and 720px height sizes), we :

  



  

  1. Process input video and obtain 1 output video at a time, and let all the cores work at the same time at 100% ;

  


  2. Process the video to obtain all output videos in parallel, by bounding each output video to a single processor core which'll work at 100% ;

  


  



  So the question is actually reduced to the parallelism efficiency of the ffmpeg program.

  



  This means that letting ffmpeg process the task procVideo - which takes 1 input video to produce 1 single output video (transcoding/downscaling and so on) - on N processor cores doesn't mean it finish the task N times faster than letting it run the same task bound to a single core. So if the efficiency is smaller than 100%, it's better to have N procVideo tasks in parallel, each bound to a single core, rather than doing the task sequentially for each output video.

  



  ---

  



  Codecs

  



  Other than the above performance problem, the usage of codecs bugs me. I am trying to obtain mp4 videos because of the wide implementation of the format in html5 browsers.

  



  So having a video as input in any format, I want to convert it to mp4. So I'm using libx264 codec with aac.

  



  

  • Use libx264, x264 or h264 for video encoding/decoding ?

  


  • Use libfdk_aac, libaacplus or aac for audio encoding/decoding to aac ?

  


  



  Also, I would like to know what are the licesing fees for each of the above codec, as the online resources on these are quite limited / hard to understand.

  



  If anyone could shed some light on those questions, I would really be grateful ! Thanks for your time !

  


• Invalid data found when processing input with compiled version of ffmpeg

  29 mai 2020, par Diego Gomez

  I am trying to use ffmpeg in an small POC. I based my code on Skia (https://github.com/google/skia/blob/master/experimental/ffmpeg/SkVideoDecoder.h)

  



  The problem is that if I open the video (mp4) with ffmpeg that comes in the operating system (macos) it works perfect, I am able to retrieve the information, framerate, length, etc

  



  On the other hand, when I try to compile and use ffmpeg in my own code, when I read the stream of the file it is returning error -1094995529 "Invalid data found when processing input"

  



  The error is happening here : https://github.com/google/skia/blob/master/experimental/ffmpeg/SkVideoDecoder.cpp#L372 (I based my code in this method)

  



  I checked ffmpeg documentation and it seems to be correct.

  



  This are my compilation flags for ffmpeg :
—disable-programs —disable-static —disable-yasm —disable-doc —enable-pic —enable-runtime-cpudetect —enable-shared —enable-small

  



  All codecs, demuxers and protocols are there :

  



  https://gist.github.com/diegoalejandrogomez/7f1446efbdd78c9654db6d6410a2c152

  



  Any ideas of what is going on ?

  



  Edit : Adding some code to make it easier to visualize :

  



  bool test::loadStream(std::unique_ptr<skstream> stream) {&#xA;    this->reset();&#xA;    if (!stream) {&#xA;        return false;&#xA;    }&#xA;    this->reset();&#xA;    int bufferSize = 4 * 1024;&#xA;    uint8_t* buffer = (uint8_t*)av_malloc(bufferSize);&#xA;    if (!buffer) {&#xA;        return false;&#xA;    }&#xA;&#xA;    fStream = std::move(stream);&#xA;    fStreamCtx = avio_alloc_context(buffer, bufferSize, 0, fStream.get(),&#xA;                                    skstream_read_packet, nullptr, skstream_seek_packet);&#xA;    if (!fStreamCtx) {&#xA;        av_freep(buffer);&#xA;        this->reset();&#xA;        return false;&#xA;    }&#xA;&#xA;    fFormatCtx = avformat_alloc_context();&#xA;    if (!fFormatCtx) {&#xA;        this->reset();&#xA;        return false;&#xA;    }&#xA;    fFormatCtx->pb = fStreamCtx;&#xA;&#xA;    int err = avformat_open_input(&amp;fFormatCtx, nullptr, nullptr, nullptr);&#xA;    if (err &lt; 0) {&#xA;        //Here is where it fails!&#xA;        SkDebugf("avformat_open_input failed %d\n", err);&#xA;        return false;&#xA;    }&#xA;</skstream>

  



  Reset :

  



  if (fFrame) {
    av_frame_free(&fFrame);
    fFrame = nullptr;
}
if (fDecoderCtx) {
    avcodec_free_context(&fDecoderCtx);
    fDecoderCtx = nullptr;
}
if (fFormatCtx) {
    avformat_close_input(&fFormatCtx);
    fFormatCtx = nullptr;
}
if (fStreamCtx) {
    av_freep(&fStreamCtx->buffer);
    avio_context_free(&fStreamCtx);
    fStreamCtx = nullptr;
}

fStream.reset(nullptr);
fStreamIndex = -1;
fMode = kDone_Mode;


  



  I have also tried with my custom read and seek method but I am getting the same error.

  


• Best practices for video storage / processing [closed]

  9 juin 2020, par Jared Tangir

  I am building an app that allows users to upload video submissions for specific events. The video file is handled with django-videokit which uses ffmpeg and mediainfo to get the dimensions, length, mimetype, and create a thumbnail. It then sends the video to a celery task to create an mp4. I am using a digitalocean droplet, nginx, and gunicorn to serve the website. Originally, I was storing, serving and processing all the videos from the droplet. I recently moved my static and media files to a Spaces bucket and use django-storages. It seems like a sacrificed a lot of speed on the uploads for what I think is the "greater good".

  



  After moving to the CDN, when the file upload reaches 100% the page sits idle with the loading wheel while I assume it sends the file to the CDN ? What is the best way to manage storage and processing of large video files ?