Allow Key Interval Setting of 1/2 Second

[Boildown]

This is for people who want to upload to YouTube, as there was a discussion on this in a recent thread.

From https://support.google.com/youtube/answer/1722171 :

GOP of half the frame rate.

This means a .5 second key interval. Right now the key interval can only be set to full second increments. I don't think there's a need for 1.5, 2.5, 3.5, etc. key intervals, just .5s for the YouTube special case.

Alternatively a custom "tune" with all the YouTube settings. I.e. Force CABAC even if UltraFast is selected, 2 b frames, .5 second keyint, High Profile, 48000 AAC, etc.

 

[paibox]

Just set your keyint manually in the custom x264 encoder settings textbox. This sounds amazingly awful in every single way, h.264 is not designed to work using settings like these, not even with the (under normal circumstances) somewhat generous bit rate recommendations for each resolution.

 

[Sapiens]

People who want to upload to Youtube should be doing a high quality/high bitrate local recording first and then re-compressing it to a more upload-friendly size that meets Youtube's specifications afterward using Handbrake or StaxRip or whatever. Having OBS output the file to be uploaded sounds like the worst way to do things.

I don't know of a way to switch from CAVLC back to CABAC when --no-cabac is called by the ultrafast preset, it would probably be a matter of setting the superfast preset instead and then manually changing individual settings back to what ultrafast uses.

 

[Sapiens]

I did a pair of test videos, see if you can spot a quality difference between the two. I can't.

http://www.youtube.com/watch?v=nuAqeaL9jmk
http://www.youtube.com/watch?v=3Xrm0cSpIi0

 

[Boildown]

People who want to upload to Youtube should be doing a high quality/high bitrate local recording first and then re-compressing it to a more upload-friendly size that meets Youtube's specifications afterward using Handbrake or StaxRip or whatever. Having OBS output the file to be uploaded sounds like the worst way to do things.

I agree, but clearly some people take their OBS output and upload it directly to YouTube, and then (maybe) edit it further there.

I don't know of a way to switch from CAVLC back to CABAC when --no-cabac is called by the ultrafast preset, it would probably be a matter of setting the superfast preset instead and then manually changing individual settings back to what ultrafast uses.

With "cabac=1"? Custom parameters override tune settings which override preset settings which override the defaults, which are identical to the medium preset. So the UltraFast preset itself sets cabac=0, my proposed fake "tune" would set it back to 1.

I did a pair of test videos, see if you can spot a quality difference

I'm fairly certain they're doing it that way so people can play videos at "any" moment in time. instead of being forced to pick up playback at a key interval or seeing graphics glitches until the next key interval hits when they skip around in the timeline.

 

[Sapiens]

ultrafast preset sets --no-cabac, not --cabac 0. I'm not sure if there is a --cabac command that can be 1/0 and set in OBS to override it. Have you done this successfully? I tried something similar a while back using the faster preset with the goal of enabling mixed-refs, but --no-mixed-refs was called and mixed-refs=1 didn't override it either, presumably because a --mixed-refs command doesn't exist.

 

[Boildown]

ultrafast preset sets --no-cabac, not --cabac 0. I'm not sure if there is a --cabac command that can be 1/0 and set in OBS to override it. Have you done this successfully? I tried something similar a while back using the faster preset with the goal of enabling mixed-refs, but --no-mixed-refs was called and mixed-refs=1 didn't override it either, presumably because a --mixed-refs command doesn't exist.

I haven't tried it for CABAC, but I have for other things. Its from here: http://dev.beandog.org/x264_preset_reference.html

 

[Sapiens]

Which setting were you able to override successfully and how did you do it? Maybe I could have simply used --mixed-refs by itself instead of also trying to set it to 1/0. I'm referring specifically to settings that are enabled by default and disabled with a "--no-" switch like --no-deblock, --no-mbtree, etc.

 

[Boildown]

Which setting were you able to override successfully and how did you do it? Maybe I could have simply used --mixed-refs by itself instead of also trying to set it to 1/0. I'm referring specifically to settings that are enabled by default and disabled with a "--no-" switch like --no-deblock, --no-mbtree, etc.

There seems to be some syntax questions between what's used with something like ffmpeg at the command line and that which is used in Handbrake, and I presumed OBS. Anyone know which is the correct syntax? --no-XXXX or XXXX=0 , for OBS? I'm out of town for the holidays so I can't really test atm.

 

[dodgepong]

For OBS, it's "key=value". So for keyint, it's keyint=15 for example.