[x264-devel] interlace

[Jason Garrett-Glaser]

On Wed, May 26, 2010 at 10:54 AM, Nageswara Gunupudi
<Nageswara.Gunupudi at harmonicinc.com> wrote:
> Hi,
>  I tried to use the --tff to encode interlace content in two passes. Surprisingly, there is about 2.84dB PSNR drop from first pass to second pass. Is it due to a possible bug in second pass encoding.
>
> Following are the encoding options I used in my testing.
> x264.exe -v --psnr -p 1 --bitrate 1500 --keyint 250 --tff --preset slow -o out.flv in_720x480_.yuv
> x264.exe -v --psnr -p 2 --bitrate 1500 --keyint 250 --tff --preset slow -o out.flv in_720x480_.yuv
>
> Please let me know if it is known issue.

x264 only enables most of its psy optimizations on the second pass, so
PSNR is expected to be lower.  If you want to optimize for PSNR at the
expense of the actual video quality, use --tune psnr.

Also make sure the bitrates match up; the first pass often ends up
with a much higher bitrate than the target on very short encodes.

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