Mistake in ffmpeg's docs for yadif
|Reported by:||Pavlo||Owned by:|
|Blocking:||Reproduced by developer:||yes|
|Analyzed by developer:||yes|
Docs describe the values for yadif's parity parameter the other way around.
ffmpeg version: N-31706-g335bbe4
I've checked main git branch and docs are still like in the version I've used.
Attached test file: dv-bff.avi
This is a short sample of video captured from JVC camcorder through IEEE1394 with the help of Windows Import Video on Windows Vista. This is DV video and it must be interlaced with bottom-field-first (BFF) field order as stated in many places, e.g here http://avisynth.org/mediawiki/Interlaced_fieldbased#About_DV_.2F_DVD_in_relation_to_field_dominance.
How to test for error:
apply yadif with BFF (according to ffmpeg's yadif docs), field separation and doubling the framerate:
ffmpeg -i dv-bff.avi -vf yadif=1:0 -r 50 output.avi
You will get a jagged video, although by applying yadif=1:1 (which, according to the docs, is top-field-first) you get a smooth playback.
I have tripple-checked the parity with other tools. GSpot video analysis software reports it to be BFF. If you play tricks similar to the one above with VirtualDub and mplayer, the results also point that the video is BFF. In fact, applying the same yadif parameters in mplayer and ffmpeg results in the same behaviour, athough according to their respective docs the meaning of parity values 0 or 1 is exactly opposite. The auto parity recognition of ffmpeg works fine though - video encoded with yadif=1:-1 plays smoothly.
I have also checked this with DVD interlaced source, which, according to thishttp://avisynth.org/mediawiki/Interlaced_fieldbased#About_DV_.2F_DVD_in_relation_to_field_dominance, must be top-field-first. The result is similar to DV case - Gspot reports TFF, mplayer's yadif plays it nice with TFF, but ffmpeg's yadif plays it nice with BFF as per docs.
As summary I strongly suspect the mistake in ffmeg's docs for yadif filter - there the explanations of meanings for the field parity parameter should be swapped. I made a corresponding patch to filters.texi file and attached it here.
Change History (7)
comment:1 by , 12 years ago
|Analyzed by developer:||set|
|Reproduced by developer:||set|
|Status:||new → closed|