On Thu, 6 Apr 2006, Nicolas wrote:
> And unfortunately, I now get a frame data under-runs, which I did not
> have before. The problem occurs only if I use the -q option in the mpeg2enc
I think the problem is the same - but the symptom has shifted slightly
because the input is (slightly) different.
> I tried the following mplex commands, with no more luck:
> mplex -f 8 02.ac3 02.m2v -o 02_r.mpeg
> mplex -f 8 -V -r 10404 02.ac3 02.m2v -o 02_r.mpeg
> ++ WARN: [mplex] Stream e0: data will arrive too late sent(SCR)=477476
> required(DTS)=477419
> ++ WARN: [mplex] Audio bd: buf= 11869 frame=000173 sector=00000077
> ++ WARN: [mplex] Video e0: buf= 79782 frame=000129 sector=00000447
> INFO: [mplex] STREAM bd completed @ frame 17656.
> INFO: [mplex] Scanned to end AU 14125
> INFO: [mplex] No. Pictures : 14126
> INFO: [mplex] No. Groups : 942
> INFO: [mplex] No. I Frames : 942 avg. size 68465 bytes
> INFO: [mplex] No. P Frames : 13184 avg. size 44546 bytes
> INFO: [mplex] No. B Frames : 0 avg. size 0 bytes
> INFO: [mplex] Average bit-rate : 9228000 bits/sec
> INFO: [mplex] Peak bit-rate : 9768800 bits/sec
> INFO: [mplex] BUFFERING min 17 Buf max 235543
> **ERROR: [mplex] MUX STATUS: Frame data under-runs detected!
> Any clue?
Yep ;)
It seems that the stream is slightly high in bitrate. This is a good
example of why leaving some "headroom" (not pusing things up to the
maximum limits) is a good idea.
Look at the peak rate of 9768800
9768800 + 224000 (audio) = 9992800
Now I use 2.5% as the overhead in a "VOB" stream so
9992800*1.025 = 10242620
and that is over the 10.08 megabits/sec for the DVD format "-f 8".
Mplex is detecting that the VBV buffer size is not sufficient to
accomodate the input streams.
IF that analysis is correct (and I'm not way off-base which has
been known to happen ;)) then all that's needed is to get the
average bitrate down another ~160 kbits/sec.
Couple things to try - could change the bitrate to '-b 9400'. OR
try adding "-E -10" to the mpeg2enc - that enables the 'single
coefficient elimination' rules at a moderate threshold, I have seen
that lower the average bitrate 10% without (visibly) degrading the
image.
Good Luck!
Cheers,
Steven Schultz
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