When chromecasting from UWP transcoded video has poor quality

Hi,

Thanks for the report.

Please share full verbose logs of both UWP transcoding with poor quality and VLC desktop transcoding with normal quality.

Thanks.

Sorry for delay with this. Added WinForms chromecast sample to https://github.com/vlasenkoalexey/LibVLCSharp.UWP.Sample_chromecast repro.

Here are logs for WinForms and UWP: https://github.com/vlasenkoalexey/LibVLCSharp.UWP.Sample_chromecast/blob/master/chromecast.uwp.log.txt https://github.com/vlasenkoalexey/LibVLCSharp.UWP.Sample_chromecast/blob/master/chromecast.winforms.log.txt

For some reason different transcoding codecs are used.

UWP: stream_out_transcode: creating video transcoding from fcc="mp4v" to fcc="VP80"
WinForms: stream_out_transcode: creating video transcoding from fcc="mp4v" to fcc="h264"

And the quality of UWP transcoded video is way worse than for WinForms. Any suggestions how to make transcoded video quality better for UWP?

Any suggestions how to make transcoded video quality better for UWP?

Fixing vlc-winrt!8 would probably help. Contribution welcome.

Fixing x264 build would probably solve this, but way beyond level of my expertise.

I looked more at logs, and as far as I understand VLC is trying to use different transcoding codecs before it fallback to VP8:

LibVLC -> main: set config option: sout-vpx-quality-mode to 1
LibVLC -> main: set config option: sout-transcode-venc to vpx{quality-mode=1}

According to https://wiki.videolan.org/VLC_command-line_help sout-vpx-quality-mode=2 is the best quality. I tried setting those flags as VLC parameters, but it didn't help.

List<string> options = new List<string>(eventArgs.SwapChainOptions);
options.Add("--verbose=3");
options.Add("--aout=winstore");
options.Add("--avcodec-fast");
options.Add("--subsdec-encoding");
options.Add("--sout-chromecast-conversion-quality=0");
options.Add("--sout-vpx-quality-mode=2");
options.Add("--sout-transcode-venc=vpx{quality-mode=2}");

@mfkl do you have any idea how to change those default options for transcoder?

See https://wiki.videolan.org/VLC_command-line_help

Transcode stream output (stream_out_transcode)
   Video:
      --sout-transcode-venc={any,jpeg,png,x264,x265,opus,g711,araw,theora,vorbis,twolame,schroedinger,substx3g,webvtt,speex,flac,t140,avcodec,lpcm,dvbsub,vpx,rtpvideo,dmo,edummy,stats,qsv,none} 
                                 Video encoder
          This is the video encoder module that will be used (and its
          associated options).
      --sout-transcode-vcodec=<string> 
                                 Destination video codec
          This is the video codec that will be used.

I tried setting those flags as VLC parameters, but it didn't help.

I'm not sure about what's wrong. If it's the syntax, check the logs, and how users format the string on various github projects.

Closing as duplicate of #215 (#215 was opened before this)

closed

reopened

Fixing x264 would address this issue, also I think there is another solution.

I found that when x264 codec is not available VLC fallbacks to VPX, and VPX has quality setting hardcoded: https://code.videolan.org/videolan/vlc-3.0/-/blob/master/modules/stream_out/chromecast/cast.cpp#L906

It'd make sense to make it dependent on sout-chromecast-conversion-quality similarly to x264. I tried to make this change, but couldn't build libvlc. The instructions https://code.videolan.org/videolan/vlc-winrt#libvlc are outdated and docker container is broken. Tried fixing it, but got bunch of other errors during build. Are there more recent instructions?

Would it make sense to change this? I can submit PR, but can't test that it works as expected and that VPX can transcode on the fly with better quality settings.

The instructions https://code.videolan.org/videolan/vlc-winrt#libvlc are outdated and docker container is broken. Tried fixing it, but got bunch of other errors during build. Are there more recent instructions?

The CI seems to build libvlc UWP 3.x OK: https://code.videolan.org/videolan/vlc-3.0/-/jobs/482838

All the instructions are located in https://code.videolan.org/videolan/vlc-3.0/-/blob/master/extras/ci/gitlab-ci.yml

Would it make sense to change this?

I don't know, you will have to ask core devs that own the chromecast code.

I can submit PR

No PR for core changes, only mailing list patches https://mailman.videolan.org/pipermail/vlc-devel/

Rebuilt LibVLC and hardcoded "venc=vpx{quality-mode=2}" for VP transcoder. Quality got a bit better, but some videos started to hiccup when played over WIFI. So it is not worth doing it. Looks like there is no way to make it work properly without x264 codec.

Sent out vlc-winrt!18 with instructions how to build LibVLC in CI docker container.

When chromecasting from UWP transcoded video has poor quality

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Does it work on other plaforms? Does it work with the official VLC apps?

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