Keep OpenH264 iMaxBitrate unspecified.
Max encoder bitrate in WebRTC and OpenH264 are different settings. In
WebRTC it is a cap for encoder target bitrate whilst in OpenH264 it is
a peak bitrate. I.e. OpenH264 is allowed to produce bitrate up to
iMaxBitrate for short time interval. That is not what WebRTC expects.
https://webrtc.googlesource.com/src/+/5ee6967c4edc667688d736c27db6f2e7be00dd0a
disabled encoders re-initialization on min/max bitrate change. Reinit of
some HW encoders takes hundreds of milliseconds and causes video freeze.
I missed that max bitrate is used by OpenH264. This caused regression
described in webrtc:11543.
This change sets iMaxBitrate=UNSPECIFIED_BIT_RATE (which is the default
value). Settings iMaxBitrate=UNSPECIFIED_BIT_RATE disables the frame
dropping logic based on that parameter. But the encoder still will drop
frames based on buffer fullness, https://source.chromium.org/chromium/chromium/src/+/master:third_party/openh264/src/codec/encoder/core/src/ratectl.cpp;l=806-807
Bug: webrtc:10773, webrtc:11543
Change-Id: I728be49e0df8a0d9a8f4438299e4c7b4c1497a78
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/174745
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31192}
diff --git a/modules/video_coding/codecs/h264/h264_encoder_impl.cc b/modules/video_coding/codecs/h264/h264_encoder_impl.cc
index ffe852b..af36dd9 100644
--- a/modules/video_coding/codecs/h264/h264_encoder_impl.cc
+++ b/modules/video_coding/codecs/h264/h264_encoder_impl.cc
@@ -542,7 +542,9 @@
encoder_params.iPicWidth = configurations_[i].width;
encoder_params.iPicHeight = configurations_[i].height;
encoder_params.iTargetBitrate = configurations_[i].target_bps;
- encoder_params.iMaxBitrate = configurations_[i].max_bps;
+ // Keep unspecified. WebRTC's max codec bitrate is not the same setting
+ // as OpenH264's iMaxBitrate. More details in https://crbug.com/webrtc/11543
+ encoder_params.iMaxBitrate = UNSPECIFIED_BIT_RATE;
// Rate Control mode
encoder_params.iRCMode = RC_BITRATE_MODE;
encoder_params.fMaxFrameRate = configurations_[i].max_frame_rate;
