[MEncoder-users] Experiences of video encoding

[Nicolas George]

Le sextidi 6 germinal, an CCXV, Corey Hickey a écrit :
> The benefit of using B-frames, as I understand it, is that you can use 
> slightly higher quantizers with them, which lets other frames have 
> slightly lower quantizers. If you specify a fixed quantizer, the three 
> codecs you tested behave differently.
<snip>
> Lavc uses the same quantizer for all three frame types, completely 
> negating the benefit of using B-frames. As I recall, constant-quantizer 
> encoding with B-frames in lavc is actually harmful. A quick test 
> supports that.

You are right, I was not aware of that.

> As you can see, bitrate goes up and PSNR goes down.

That surprises me: some tests I did last summer, which were a prelude to
these tests, showed that even with lavc, B-frames increase quality.

The best solution would be for me to make a set of tests varying the
B-frames and quantizer offset options. But for now, I will invest my time
and my CPU power in tests for x264.

<snip>

> I want to reiterate that I know how much work this involves; don't get 
> discouraged!

Thanks, and thanks for your remarks: I will keep them safely for future
reference. But I do not think that this fine-tuning can be enough for lavc
to beat x264, therefore I will keep working on the latter for now.

If I have time later, I may re-start the whole set of lavc sets taking your
remarks into account.

Regards,

-- 
  Nicolas George
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