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Ogg Theora video transcodes show heavy compression artifacts (bad bitrate/resolution ratio)
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Description

Ogg Theora transcodes use the same bitrates as WebM/VP8 transcodes, which results in the older, less efficient Theora encoding producing a lot of visible compression artifacts in scenes with a lot of motion.

For example File:Eisbach_surfen_v1.ogv looks absolutely terrible in our 360p Ogg transcode:

whereas the same-bitrate, same-resolution 360p WebM transcode looks ok:

Screenshots of almost the same frame in each (Ogg left, WebM right):

I recommend shifting the bitrates one step over for Ogg:

  • double 480p from 1024k to 2048k
  • double 360p from 512k to 1024k
  • add 240p at 512k

This'll put the 240p Ogg at the same bitrate as the 360p WebM, the 360p Ogg at about the same bitrate as the 480p WebM, etc. In my testing this brings the picture quality at the same resolution in Ogg much closer to the WebM quality, even for high-motion scenes like this pathological case.

For bandwidth-limited streaming (which isn't even implemented in any automated fashion yet) the player should be using the bandwidth as a filter anyway, which would shift players down one resolution scale but give higher picture quality at the lower resolution.

Details

Related Gerrit Patches:
mediawiki/extensions/TimedMediaHandler : masterIncrease quality of Ogg Theora video transcodes

Event Timeline

brion created this task.Jul 26 2015, 8:19 PM
brion raised the priority of this task from to Needs Triage.
brion updated the task description. (Show Details)
brion added a subscriber: brion.
Restricted Application added a project: Multimedia. · View Herald TranscriptJul 26 2015, 8:19 PM
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Change 227155 had a related patch set uploaded (by Brion VIBBER):
Increase quality of Ogg Theora video transcodes

https://gerrit.wikimedia.org/r/227155

Restricted Application added a subscriber: Matanya. · View Herald TranscriptJul 26 2015, 8:29 PM

Change 227155 merged by jenkins-bot:
Increase quality of Ogg Theora video transcodes

https://gerrit.wikimedia.org/r/227155

brion closed this task as Resolved.Aug 9 2015, 4:15 PM
brion claimed this task.

Ok this went out last week; resolving. Old transcodes will be re-run by a bot over time (T104061)...