Transcode "Bitrate" setting fails VLC 2.1.3 (64b) Win7 64b
Posted: 11 May 2014 23:04
I am running VLC 2.1.3 (64bit) on WIndows 7 64 bit.
I have no information as to whether this issue is specific to WIndows, or a general VLC issue.
Details of problem:
Attempting to transcode MPEG2 to MPEG2 (to reduce the bitrate / filesize) I found that the video "bitrate" field had no effect - but it is not greyed-out, so presumably it should do something.
This is found under Encoder Options when editing the conversion profile in the Convert Menu.
I also tried setting "Video bitrate tolerance" in the global Advanced Preferences (Input/Codecs -> Video Codecs -> FFMpeg), as I thought that maybe when set to 0 (default) it might disable the "bitrate" setting.
But this had no effect at all, regardless of "bitrate".
I also tried setting FFMpeg "Rate control buffer size", but could find no value which worked.
All the values I tried from 1kB to 10000kB resulted in an error message about "can't find encoder" (!) and no video was produced.
However it had no problem with the encoder if "Rate control buffer size" was left at 0 (default setting).
I could find no combination which had any effect on the output bitrate.
This issue seems very similar to the problem in my previous post about transcoding failing when the "video scaling filter" is selected in the profile with MPEG2 transcoding (forum.videolan.org/viewtopic.php?f=14&t=119173).
Additional comment:
It is not clear what "bitrate" is attempting to set.
Actually in most cases there should really be more than one parameter.
ie:
- maximum instantaneous bitrate (which affects playback / decoding buffer) and
- target average bitrate (which determines file size)
ffmpeg preferences has "video bit rate tolerance". But I could find no "target bitrate" preference, only the parameter in the profile.
Other encoders have different parameters to achieve broadly the same thing, but they are not referenced in the profile either.
I have no information as to whether this issue is specific to WIndows, or a general VLC issue.
Details of problem:
Attempting to transcode MPEG2 to MPEG2 (to reduce the bitrate / filesize) I found that the video "bitrate" field had no effect - but it is not greyed-out, so presumably it should do something.
This is found under Encoder Options when editing the conversion profile in the Convert Menu.
I also tried setting "Video bitrate tolerance" in the global Advanced Preferences (Input/Codecs -> Video Codecs -> FFMpeg), as I thought that maybe when set to 0 (default) it might disable the "bitrate" setting.
But this had no effect at all, regardless of "bitrate".
I also tried setting FFMpeg "Rate control buffer size", but could find no value which worked.
All the values I tried from 1kB to 10000kB resulted in an error message about "can't find encoder" (!) and no video was produced.
However it had no problem with the encoder if "Rate control buffer size" was left at 0 (default setting).
I could find no combination which had any effect on the output bitrate.
This issue seems very similar to the problem in my previous post about transcoding failing when the "video scaling filter" is selected in the profile with MPEG2 transcoding (forum.videolan.org/viewtopic.php?f=14&t=119173).
Additional comment:
It is not clear what "bitrate" is attempting to set.
Actually in most cases there should really be more than one parameter.
ie:
- maximum instantaneous bitrate (which affects playback / decoding buffer) and
- target average bitrate (which determines file size)
ffmpeg preferences has "video bit rate tolerance". But I could find no "target bitrate" preference, only the parameter in the profile.
Other encoders have different parameters to achieve broadly the same thing, but they are not referenced in the profile either.