Re: [rtcweb] Cross-check of Google VP8 vs H.264 comparison

Sergio Garcia Murillo <> Thu, 14 March 2013 20:43 UTC

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Date: Thu, 14 Mar 2013 21:43:41 +0100
From: Sergio Garcia Murillo <>
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Subject: Re: [rtcweb] Cross-check of Google VP8 vs H.264 comparison
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I also cross-posted the x264 encoding parameters used in the comparison 
in the x264-devel list:

>/  What would be the best encoding parameters for x264 in these scenario?
1.  Set the slowest preset you're willing to tolerate.
2.  Set --tune to psnr or ssim (based on the one you're testing).
3.  Since they're doing CBR streaming for WebRTC, they need to set
appropriate ratecontrol settings.  Some examples:
1 second of latency: --vbv-maxrate $b --vbv-bufsize $b
0.25 seconds of latency: --vbv-maxrate $b --vbv-bufsize $b/4
low latency streaming with capped frame size: --vbv-maxrate $b
--vbv-bufsize $b/fps

In addition, if they care about latency, they'd want to make sure both
encoders are set with appropriate low-latency settings.  They'd also
need to verify how well both encoders are abiding by these

Best regards

El 14/03/2013 19:13, Bo Burman escribió:
> Hi,
> As said on the microphone today, we have cross-checked Google's VP8 vs H.264 comparison. Google reported bit rate gains for VP8 of 19%. However, the H.264 was at an unfair advantage due to the fact that the --tune psnr flag was not used in x264. This should of course be used when doing psnr-measurements. For vp8, this flag is set to psnr by default.
> When re-running the tests with --tune psnr for x264, and using version 130 of x264 instead of version 128 that was used in the Google test, the difference disappeared (1% difference).
> Cheers,
> Bo
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