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[Savannah-cvs] [777] Use more properly researched ffmpeg settings


From: iank
Subject: [Savannah-cvs] [777] Use more properly researched ffmpeg settings
Date: Mon, 1 Apr 2024 22:08:21 -0400 (EDT)

Revision: 777
          
http://svn.savannah.gnu.org/viewvc/?view=rev&root=administration&revision=777
Author:   iank
Date:     2024-04-01 22:08:19 -0400 (Mon, 01 Apr 2024)
Log Message:
-----------
Use more properly researched ffmpeg settings

Removed useless options:

* cluster_time_limit=5100 cluster_size_limit=2M: these come from a very
  old xiph.org wiki page, it claims that once upon a time they were
  needed for icecast compatibility. Nowadays, they are undocumented in
  ffmpeg, but greping source code, they are used in dash and mkv, not
  the webm we are using.

* minrate=1.5M maxrate=1.5M, found some reference to say say this pushes
  vpx into stricter cbr mode, but it is unclear if that is actually
  true. Most sources do not recommend this when using realtime, and I
  suspect it is largely superflous and not beneficial.

* crf=30 this does nothing in the mode we are using.

Modified Paths:
--------------
    trunk/sviki/fsf/tools/OBS.mdwn

Modified: trunk/sviki/fsf/tools/OBS.mdwn
===================================================================
--- trunk/sviki/fsf/tools/OBS.mdwn      2024-04-01 12:46:17 UTC (rev 776)
+++ trunk/sviki/fsf/tools/OBS.mdwn      2024-04-02 02:08:19 UTC (rev 777)
@@ -50,18 +50,22 @@
 * File path or URL: 
`icecast://source:PASSWORD@live-master.fsf.org:8000/stream-room-NAME.webm`
   * Note: Password has an O as in Opal.  Not a zero.
 * Container format: `webm`
-* Muster settings (if any): `content_type=video/webm cluster_time_limit=5100 
cluster_size_limit=2M`
+* Muster settings (if any): `content_type=video/webm`
 * Video Bitrate: `1500 Kbps`
-* Keyframe interval (frames): `150`
+* Keyframe interval (frames): `60`
 * Rescale Output: greyed out, not settable.
 * Show all codecs (even if potentially incompatible): checked
 * Video Encoder: `libvpx`
-* Video Encoder Settings (if any): `rt cpu-used=5 threads=2 error-resilient=1 
crf=30 g=150 minrate=1.5M maxrate=1.5M`
+* Video Encoder Settings (if any): `quality=realtime cpu-used=5 threads=2 
error-resilient=1`
+** For vp9, which we will test in LP2024: `quality=realtime cpu-used=5 
threads=4 row-mt=1 tile-columns=2 frame-parallel=1`
+** background notes: man ffmpeg-codecs says -g is group of picture size, but 
online sources call it the "keyframe interval."  In vp9, at roughly > 2 seconds 
worth of frames, it starts to increase latency at a corresponding rate. If cpu 
struggles, adjust cpu-used upward, max is 8 which uses the lowest cpu.
 * Audio Bitrate: `96 Kbps`
 * Audio Track: check mark on 1.
 * Audio Encoder: `libvorbis`
 * Audio Encoder Settings (if any): empty
 
+
+
 #### Audio
 
 * Desktop Audio: (Set to your output device such that you see sound levels 
when there is audio playing on your system)




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