Recherche avancée

Sur d’autres sites (5922)

• Can you think of a reason why windows might not enable audio if noone is logged in ?

  3 juillet 2017, par Caius Jard

  I’m having a bizarre problem with some virtual servers created to record podcasts. They run on amazon AWS as windows server 2012 instances and a small c# app tells FFMPEG to do the heavy lifting of capturing from the virtual screen and reading from the virtual sound card (Virtual Audio Cable : https://en.wikipedia.org/wiki/Virtual_Audio_Cable) via DirectShow filters

  The problem I have is if I leave the machine to do its stuff unattended, the recordings are sometimes silent. If I log in via VNC and watch it doing its stuff the audio is recorded just fine. All other aspects of the test op are the same, and the virtual machine is shut down between successive recordings so each one should theoretically be a clean slate. The app runs under a logged in session (hence the use of VNC rather than RDP)

  I’m now wondering if there is some optimisation of the windows sound engine whereby it doesn’t bother playing audio if it thinks noone is listening. The confusing thing to me is that not every virtual machine suffers these problems ; some of them record fine (and they’re all created from the same seed virtual hard disk image) in unattended mode

  I’m asking this question with the aim of getting together a list of things I can check/look into/debug.. I don’t have much knowledge of how MME/DirectSound/WASAPI work internally...

• FFmpeg dxva2 H264 decoder reinitialize codec - access violation

  18 janvier 2023, par Spuriga

  I have a small project which decodes h264 I frame (SPS+PPS in extradata).
It uses "dxva2" hw acceleration and works fine until I reinitialize the codec. This can be occured when an rtsp stream change the format. Fe. : h264 to h264H. and the extradata must be changed.

  


  The extradata modifying code is :

  


      ...

    ret = decode_write(decoder_ctx, packet);          //GOOD    
    ret = decode_write(decoder_ctx, NULL);

    if (avcodec_close(decoder_ctx) < 0)
        return -2;

    if (hw_decoder_init(decoder_ctx, type) < 0)
        return -1;

    if ((ret = avcodec_open2(decoder_ctx, decoder, NULL)) < 0) {
        fprintf(stderr, "Failed to open codec for stream.\n");
        return -1;
    }

    ret = decode_write(decoder_ctx, packet);         //ACCESS VIOLATION
    ret = decode_write(decoder_ctx, NULL);


  


  The next avcodec_send_packet goes access violation exception.
When I switch off the HW acceleration and fallback to CPU this change is works fine.

  


  So the only problem when I use dxva2 and reinitialize the codec.

  


  The extradata change code is not in this small example, because the error reason is the reinitialize.

  


• Ffmpeg can't open m3u8 link

  23 janvier 2021, par Andrei Iosifescu

  Ffmpeg can't play https://live.webcamromania.ro/WR051/wrcam_051/playlist.m3u8. It gives an Input/Output error. With other links it works fine.