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Bug 645157 - avenc_mpeg2video: fix defaults for video encoders
avenc_mpeg2video: fix defaults for video encoders
Status: RESOLVED DUPLICATE of bug 644919
Product: GStreamer
Classification: Platform
Component: gst-libav
git master
Other Linux
: Normal normal
: git master
Assigned To: GStreamer Maintainers
GStreamer Maintainers
Depends on:
Blocks:
 
 
Reported: 2011-03-18 16:22 UTC by Luis de Bethencourt
Modified: 2015-01-19 18:36 UTC
See Also:
GNOME target: ---
GNOME version: ---



Description Luis de Bethencourt 2011-03-18 16:22:59 UTC
When using ffenc_mpeg2video through encodebin the video is very blocky, it is handled with the default parameters and changing properties isn't possible without using presets.

So it has been suggested to change the default values of gst-ffmpeg's baseclass to better yet sane values. To minimize then the use of presets after that.
Comment 1 Robert Swain 2011-03-31 12:04:33 UTC
To be blunt - FFmpeg defaults suck. Perhaps those in gst-ffmpeg don't suck quite so much but considering your concerns about quality, it seems likely.

We can't just change the gst-ffmpeg property defaults though as some values are good for some codecs and other values are good for other codecs.

There are rumbles amongst libav/FFmpeg ranks that we want to move a lot of options out of AVCodecContext and into AVOption arrays per-codec.

Until that happens, I would recommend adjusting the defaults that benefit all codecs and then writing per-codec presets for the remaining options required to achieve good quality.

For MPEG-2, the command line options, '-cmp 2 -subcmp 2 -mbd 2 -trellis 1', would be a good start. Those can be translated to gst-ffmpeg properties pretty easily.
Comment 2 Robert Swain 2011-03-31 12:32:16 UTC
I can be a point of reference for this bug. Implementing one preset file for ffenc_mpeg2video wouldn't take long - most of the time is understanding syntax and testing that the preset file works.
Comment 3 Stefan Sauer (gstreamer, gtkdoc dev) 2015-01-19 12:45:40 UTC
robert, preset files are simple gkeyfiles. Search the sources for "*.prs" to find examples.
I am closing this as a dup of 644919

*** This bug has been marked as a duplicate of bug 644919 ***
Comment 4 Robert Swain 2015-01-19 16:06:29 UTC
I would argue that default parameters amount to more than bitrate. Maybe bug 644919 is a subset of this ticket. :)
Comment 5 Stefan Sauer (gstreamer, gtkdoc dev) 2015-01-19 18:36:56 UTC
Robert, feel free to swap or edit. I went by date the bug was filed.