1030109 - 8x10 OMX H.264 encoder doesn't support Constant bitrate config

Status: RESOLVED WONTFIX

(Core :: WebRTC: Audio/Video, defect)

Description

[Randell Jesup [:jesup] (needinfo me)]

+++ This bug was initially created as a clone of Bug #1015029 +++

Follow-on bug:

The 8x10 H.264 OMX encoder doesn't support OMX_Video_ControlRateConstant and you get Variable bitrate if you try to use it.  The only viable candidate is OMX_Video_ControlRateConstantSkipFrames, which is CBR with frame-skipping after an IDR to keep the bitrate average ok.

We are using ControlRateConstantSkipFrames currently, but for better motion support for Constant in the hardware/firmware would be useful.  Likely the quality would drop (more) on an IDR and for a few pframes after it to a) reduce the bitrate spike, and b) compensate for the spike over 2-4 pframes following (and perhaps longer at a more modest reduction).

This requires reworking the encode queue logic to account for the frame skipping.  There is also a bug in the encoder or stagefright where the input timestamps don't appear in the output, so the code using timestamps is ifdef'd off.

Also of interest is "how do we know if Constant is supported?"

Comment 1

[Randell Jesup [:jesup] (needinfo me)]

Our understanding is that this cannot be supported in the 8x10 platform.