xpra-html5: native video decoding errors

Sometime since e0e5de35b63eab7c5a6a6ff60827c7af0e77c2f5 (2016!)

I have added an example to enable fastdecode: ca3d1db4d9a242600bc5d86019be027ab9645617 And the xpra server will now honour it, both with h264+mp4 and mpeg4+mp4: https://github.com/Xpra-org/xpra/commit/b10da3f3291d492839843e12a08359c40cd40f8a

Note: to change which actual codec the server will choose for the html5 client in “native” video mode, using the “score-delta” for the codec chosen: 8cf87c2035ef5fca158e1126fdf362bd642f1564 (h264+mp4 is now ahead of mpeg4+mp4).

---

This command generates an h264 stream that browsers can play:

ffmpeg -f x11grab -i :99 -c:v libx264 -pix_fmt yuv420p \
    -profile:v baseline -tune fastdecode -preset ultrafast \
    -f mp4 -movflags frag_keyframe+default_base_moof -frag_duration 1 \
    pipe:1

Link: Fragmented MP4 - problem playing in browser

Comparing it with our enc_ffmpeg encoder:

• we use YUV420P (or NV12 with libva - which translates to the same subsampling)
• baseline profile since 8cf87c2035ef5fca158e1126fdf362bd642f1564
• fastdecode since b10da3f3291d492839843e12a08359c40cd40f8a
• ultrafast preset
• movflags: empty_moov+frag_keyframe+default_base_moof+faststart - IIRC, faststart is important too

---

There are a lot more fastdecode tweaks in the plain enc_x264 encoder: https://github.com/Xpra-org/xpra/blob/b10da3f3291d492839843e12a08359c40cd40f8a/xpra/codecs/enc_x264/encoder.pyx#L594-L597 https://github.com/Xpra-org/xpra/blob/b10da3f3291d492839843e12a08359c40cd40f8a/xpra/codecs/enc_x264/encoder.pyx#L634-L638 removed B frames, sliced threads, b_weighted_bipred, i_weighted_pred. Perhaps these tweaks would help with the enc_ffmpeg encoder?

---

Here is the cryptic browser error:

Error: Failed to execute 'appendBuffer' on 'SourceBuffer': This SourceBuffer has been removed from the parent media source.
    at XpraWindow._push_video_buffers (http://localhost:12000/js/Window.js:1223:7)
    at XpraWindow.paint [as do_paint] (http://localhost:12000/js/Window.js:1592:10)
    at XpraWindow.paint (http://localhost:12000/js/Window.js:1321:33)
    at XpraClient.do_process_draw (http://localhost:12000/js/Client.js:2990:7)
    at Worker.<anonymous> (http://localhost:12000/js/Client.js:433:7)
error painting mpeg4+mp4 InvalidStateError: Failed to execute 'appendBuffer' on 'SourceBuffer': This SourceBuffer has been removed from the parent media source.