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• VideoJS seekable().end(0) always returns 0

  18 septembre 2022, par Clovis Nyu

  I am trying to jump to a particular timestamp of a video, but using player.currentTime(someTime) always sends the video back to the start. Upon doing some research, I found that running player.seekable().end(0) always returns 0. I realize that this might be a problem with the fact that I'm using MP4, but I've tried using

  


  ffmpeg -i input.mp4 -c copy -movflags +faststart output.mp4


  


  to fix it and it doesn't work. Below is my code

  


  &#xA;&#xA;    &#xA;&#xA;&#xA;    <source src="http://localhost:8000/some_video.mp4" type="video/mp4"></source>&#xA;    <p class="vjs-no-js">&#xA;        To view this video please enable JavaScript, and consider upgrading to a&#xA;        web browser that&#xA;        <a href="https://videojs.com/html5-video-support/" target="_blank">supports HTML5 video&#xA;    </a></p>&#xA;&#xA;&#xA;<button>Jump</button>&#xA;&#xA;<code class="echappe-js">&lt;script src=&quot;https://vjs.zencdn.net/7.7.5/video.js&quot;&gt;&lt;/script&gt;&#xA;&lt;script&gt;&amp;#xA;    var VIDEO_JS = videojs(&amp;#x27;my-video&amp;#x27;);&amp;#xA;&amp;#xA;    function jump() {&amp;#xA;        VIDEO_JS.currentTime(10);&amp;#xA;    }&amp;#xA;&lt;/script&gt;&#xA;&#xA;

  


  For more context, the videos are taken from youtube, the audio is then split into vocals and accompaniment using spleeter, then ffmpeg is used to merge back the resulting audio files into the original video.

  


  Any help would be appreciated. Thanks !

  


• libav/ffmpeg : avcodec_decode_video2() returns -1 when separating demultiplexing and decoding

  26 avril 2013, par unbekannt

  I'm using libav (from a C++ program on Linux and Windows) to decode video streams from a file, which works fine (decoding various formats like H264 and MPEG2) using avformat_open_input(), av_read_frame() and avcodec_decode_video2().

  Now I have to separate demultiplexing and decoding. One class will call avformat_open_input() and av_read_frame() and then pass the AVPackets into a queue that is read by another class. There I use avcodec_alloc_context3() to get the AVCodecContext needed for avcodec_decode_video2(). I've tested that with a MPEG2 video stream and it works.

  Problems arise if I try to decode a H264 stream : avcodec_decode_video2() always returns -1 and outputs "no frame". I understand that additional data (SPS/PPS) is needed to decode this stream, so I've tried to replicate the original AVCodecContext from the demultiplexer in the decoder, but it won't work :

  • Copying the content of the extradata field and setting all other values that differ from the default ones in the decoder : -1 is returned
  • Using the same context (i.e. passing along the pointer) results in a crash

  I also tried to set CODEC_FLAG2_CHUNKS. avcodec_decode_video2() then always returns packet.size - 3 (??) and frameFinished is never set to 1.

  In my opinion I have a general problem here that will arise whenever settings from the original CodecContext are needed to decode the AVPackets. I'd be grateful for any hints on how to solve that problem !

  EDIT : Sometimes writing down your problem helps solving it... Using a copy of the context struct (avcodec_copy_context) and opening the codec only after receiving the copy results in decoded frames. Does anyone know if that is safe or the best way to do it ?

• Node spawn child process doesn't execute the command after exec child process in aws node 10 lambda

  29 juillet 2020, par Danielkent

  I am attempting to run 2 child processes, but one seems to be blocked and eventually times out the node lambda.

  


  Environment :

  


  

  • AWS node 10 lambda running in a docker container.

  


  • Accesses ffmpeg and ffprobe via a lambda layer in the /opt/bin directory.

  


  


  child_process.exec
I am running ffprobe in a child_process.exec to get the file format of an audio file. I am using exec because the output is a small json response (which shouldn't consume much memory).

  


  child_process.spawn
Shortly after I run ffmpeg to convert the audio file to mp3 using child_process.spawn.

  


  The problem is the FFMPEG child_process.spawn command doesn't run after ffprobe (even though ffprobe successfully completes). If I don't run the ffprobe command the FFMPEG command runs perfectly.

  


  Which leads me to believing this is an issue with how I am dealing with child processes in node.

  


  Is it possible the child_process.exec ffprobe command is somehow still running/ blocking the new ffmpeg (child_process.spawn) command from running - if so how do I check this ?

  


  When I access the running processes in the docker container only the new ffmpeg command seems to be running, although it consumes no memory and just hangs - seemingly doing nothing. I even tried launching the ffmpeg command from the docker cli (avoiding using the node env) and this works fine and runs as expected.