Re: [transcode-users] File size not governed by -w switch?

[David Liontooth <liontooth@xxxxxxxxxx>]

Andrew Church wrote:
>> As you can see, setting the video bitrate to 500 results in a huge range
>> of file sizes, from 377 to 684MB. Likewise, the 800 value produces results
>> in the range of 407 to 754MB. I'm used to using mencoder with divx, where
>> I get variations in file sizes around 1%. What's going on?
>>     
> This looks like a bug in x264, or possibly in the ffmpeg interface to
> x264; -w works fine with everything else.  
Conversely, I don't see this effect in ffmpeg used on its own; as for
mencoder, it produces x264 files of uniform size.
> (Try encoding the same source
> material at different bitrates and you should find that higher bitrates do
> indeed give larger file sizes, though not in proportion.  My guess is that
> x264 is taking the given bitrate as only a hint, rather than trying to
> match it exactly.)
>   
OK, I'll give that a try.

I'm currently running parallel encoding to h264 and divx. If what we're
seeing is simply caused by variable bit rate, I should see quality
improvements over divx for the larger transcode files. I haven't had a
chance to examine quality yet.

David