4
I am trying to create M4A files to play in my car, which has a USB interface.
This file works fine as is. However if I remux the file using:
ffmpeg -i Miaow-02-Hidden.m4a -c copy outfile.m4a
It will no longer play in my car.
Steven Penny
Posted 2013-07-07T04:34:08.083
Reputation: 7 294
4
I can the two files through TagEditor and noticed a difference:
$ tageditor --info --files Miaow-02-Hidden.m4a outfile.m4a
Technical information for "Miaow-02-Hidden.m4a":
Container format: MPEG-4 Part 14
Document type M4A
Duration 4 min 5 s 156 ms
Creation time 2010-11-03 09:42:53
Modification time 2010-11-03 09:43:12
Tag position before data
Index position before data
Padding 3.12 KiB
Technical information for "outfile.m4a":
Container format: MPEG-4 Part 14
Document type M4A
Version 512
Duration 4 min 5 s 157 ms
Creation time 1904-01-01 00:00:00
Modification time 1904-01-01 00:00:00
Tag position after data
Index position after data
Padding 8 bytes
As you can see, the original file has the index (moov atom) at the beginning of the file. This is known as faststart. I changed my command and it fixed the problem:
ffmpeg -i Miaow-02-Hidden.m4a -c copy -movflags faststart outfile.m4a
Steven Penny
Posted 2013-07-07T04:34:08.083
Reputation: 7 294
From my experience car radios tend to be very picky. Might be worth a shot asking the vendor what kinds of formats are supported, or enquiring in a product support forum. Does it work if you re-encode the audio? – slhck – 2013-07-07T07:04:57.623