EVEA H.264: Disable periodic key frames by default.

EVEA H.264: Disable periodic key frames by default.

The V4L2 default GOP size is only 12. This inserts intra frames too frequently and wastes bitrate. In practice it is not necessary for encoder to send periodic key frames.

BUG=284783
TEST=verify that EVEA only produces one I-frame initially and then all P-frames after.
R=fischman@chromium.org, sheu@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=225284

[hshi1, 2013-09-25 20:45:08]

PTAL. sheu@ - FYI. fischman@ - OWNER. Thanks!

[hshi1, 2013-09-25 20:46:22]

For reference: link to the definition of default GOP size of 12:

https://cs.corp.google.com/p#kernel/2.6.34_440/Documentation/DocBook/v4l/cont...

[Ami GONE FROM CHROMIUM, 2013-09-25 20:55:29]

Can you justify this by pointing at webrtc/libvpx defaults?
(why 60 and not 50 or 80?)

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[hshi1, 2013-09-25 21:03:12]

On 2013/09/25 20:55:29, Ami Fischman wrote:
> Can you justify this by pointing at webrtc/libvpx defaults?
> (why 60 and not 50 or 80?)
> 
> To unsubscribe from this group and stop receiving emails from it, send an
email
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I agree it is a fairly arbitrary number. The libvpx default is actually 3000 (in
other words, key frames are practically never used). See
webrtc/modules/video_coding/main/source/codec_database.cc where
settings->codecSpecific.VP8.keyFrameInterval is set. Shall I set it to 3000 as
well? I think it doesn't matter, and we shouldn't really be sending any key
frames at all unless the receiver specifically requests it.

[Ami GONE FROM CHROMIUM, 2013-09-25 21:05:14]

Yeah, matching webrtc SGTM.

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[hshi1, 2013-09-25 21:08:43]

On 2013/09/25 21:05:14, Ami Fischman wrote:
> Yeah, matching webrtc SGTM.
> 
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Done.

[sheu, 2013-09-25 21:15:03]

I'd tweak this knob in the other direction -- set to 0, which means (in MFC
firmware parlance) no I frames at all.  If WebRTC wants to force an I frame
every X frames, I'd rather have it send down a request every X frames rather
than trying to tweak this knob to match.

[hshi1, 2013-09-25 21:24:32]

On 2013/09/25 21:15:03, sheu wrote:
> I'd tweak this knob in the other direction -- set to 0, which means (in MFC
> firmware parlance) no I frames at all.  If WebRTC wants to force an I frame
> every X frames, I'd rather have it send down a request every X frames rather
> than trying to tweak this knob to match.

Good point. PTAL Patch Set #3, thanks!

[sheu, 2013-09-25 21:26:22]

lgtm, thanks

[Ami GONE FROM CHROMIUM, 2013-09-25 21:49:28]

lgtm

[hshi1, 2013-09-26 00:31:54]

Committed patchset #3 manually as r225284 (presubmit successful).