[FFmpeg-user] -qscale:a and -write_xing 0 can't be used at same time?

Moritz Barsnick barsnick at gmx.net
Fri Jan 27 19:56:00 EET 2017

On Fri, Jan 27, 2017 at 00:53:43 +0900, 桃源老師 wrote:

> I found that the result mp3 shows twice long duration in macOS Finder
> and iTunes. I googled and found that adding "-write_xing 0" fixes
> this wrong duration.

It would be interesting to see the different interpretations of
durations in various tools. But I guess you've already come to the
obvious conclusion that Mac/iTunes can't cope well with Xing headers.

> But if I try to use "-write_xing 0" with "-qscale:a 2" at same time, the resulting mp3 shows very wrong duration on macOS Finder and iTunes.
> Is -qscale:a and -write_xing 0 can't used at same time?

I checked the code, and did some experiments, and both *can* be used at
the same time. The write_xing option does make a difference to the
files I created.

What does change, is that "-qscale:a" instructs libmp3lame to use VBR
encoding, instead of ffmpeg's 128k CBR. I believe Mac/iTunes is going crazy
and getting confused by VBR. Hey, we're in the 21st century. The last
programs I saw which didn't handle VBR nicely were in the early 90s.

But that's what the Xing header is for, I guess: Not having to estimate
the duration, but being able to calculate it from the bitrate? Question
is why that also confuses Mac. OMG, what do other users do? Do files
not created by ffmpeg work for you in the finder?


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