Hello Moritz-san, Thanks for your replay:
> 2017/01/28 2:56 A.M. Moritz Barsnick <barsnick <at> gmx.net > <http://gmx.net/>> wrote: > > 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. > ;-) I made a small study about Xing headers. It's for mp3's VBR duration calculation. Please don't say "You are at there!" ;-) My understanding for ffmpeg's option "-write_xing 0" is to instruct not to write Xing header to result file(s). If it is correct, I wonder why ffmpeg's default CBR file's duration can be fixed in Mac/iTunes. Also, I feel doubt for your comment Mac/iTunes can't cope well with Xing headers. The reason is below... >> 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. > :-P > > 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? I didn't understand "what Xing header is" before receiving your replay... So I thought that the magic word "-write_xing 0" is required in anyway... But now I understand that my ffmpeg's option "-qscale:a" and "-write_xing 0" means create a mp3 file with VBR and not to write Xing header... It might be very hard to calculate duration for *any* kind of program. I now understand "-qscale:a" and "-write_xing 0" should not be used at the same time. And confirmed that Mac/iTunes understand duration correctly with "-qscale:a" only... I think this means that Mac/iTunes can handle Xing header, doesn't it? Best Regards, // Miya aka. TougenRoushi // みや aka. 桃源老師
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