Re: [transcode-users] rc buffer underflow with ffmpeg

[Phil Ehrens <phil@xxxxxxxx>]

Andrew Church wrote:
> >I was trying to use ffmpeg (instead of mpeg2enc) to encode some clips of 
> >stuff I captured & have been getting rc buffer underflow message(s).
> [...]
> >vrc_maxrate=9800
> 
>      Obvious solution: lower vrc_maxrate.  Even the default only puts it
> at 9000 kbps, and raising it farther really won't gain you anything
> noticeable.  If you continue having problems, lower it even further.  See
> also http://www.transcoding.org/cgi-bin/transcode?FFmpeg_Vs._Mpeg2enc
> 
> ># vrc_buf_size=1792 # suggestion online
> >vrc_buf_size=1835 # DVD setting in man page
> 
>      1792 is correct, leave it alone.  (The manpage you read probably used
> kbit=10^3 bits; this setting uses kbit=2^10 bits.)

Ah, after reading this, I wonder... perhaps the reason I
get tons of buffer underflows when I do 2-pass encoding
is because the ntsc_dvd profile uses -w 5000, and whereas
that does not ever produce an average bitrate anywhere
near that with single pass, maybe it really does with 2-pass,
and mucks things up? Erik, how did you decide on -w 5000 as
the default anyway?

-- 
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