[Resolved] 3.0.0-a5: Lack of ffmpeg quality control.

[Casper]

Changing the Transcoding Quality (MPEG2) in the UI is not changing the ffmpeg (FFmepg Web Video) quality parameter which is always -q:v 3. This utilizes about 30Mbps which is too much for my wireless connection.

I have resorted to using MaxVideoBitrateMbps in the renderer conf file to reduce network usage which replaces -q:v 3 with -maxrate. Strangely changing the maxrate value has no effect, it seems to be limited to only ~7Mbps despite setting the value to 100Mbps which is reflected in the debug log as -maxrate 100000000.

Is there a way to have custom options for ffmpeg like mencoder? I know of the ffmpeg.webfilters file but that is only for specific URLs.

[infidel]

Is there a way to have custom options for ffmpeg like mencoder? I know of the ffmpeg.webfilters file but that is only for specific URLs.

• I haven't actually tried it, but there's a CustomFFmpegOptions setting defined for renderer confs.
• You can also use a "specific" rule to match everything in ffmpeg.webfilters

  Code: Select all

  .* | -q:v ...

[Casper]

Thanks for the tip. CustomFFmpegOptions works, the custom options are reflected in the debug log and despite the -q option already existing, the custom one appended after overrides it.

The 'q' option (aka 'qscale') controls variable bitrate quality with value between 1-31, with 1 being the highest quality and 31 the lowest. I reduced it from 3 to 8 and the stuttering has mostly gone.

Code: Select all

CustomFFmpegOptions=-q:v 8

[ExSport]

Your custom settings was added so it overridden original one? Or original -q:v <number> was replaced by your custom setting?
For MEncoder engine what I remember custom settings rewrites default value so setting is present once. Same should be also for FFMPEG so same settings is not doubled which can make conflicts for some settings.
What is behavior right now? Thx

[Casper]

Your custom settings was added so it overridden original one?

Yes, in the case of the -q option it is overriding the original value. For example the following has very low quality as you would expect with a value of 31.

Code: Select all

-threads 6 -c:a ac3 -c:v mpeg2video -f vob -q:v 3 -q:a 3 -q:v 31

But like you say, other options may behave differently, existing options should be substituted rather than duplicated.

[SubJunk]

Thanks for reporting this, Casper. The FFmpeg Web Video engine was not paying attention to the quality settings, although the FFmpeg Video engine was. The fix should be in the next release.

[Casper]

Now that the the quality settings work perfectly in 3.0.0-b1 I strongly recommend users not to mess with CustomFFmpegOptions.