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I don't think that's quite accurate. There's no functional difference between a .m4b file and a .m4a file. Both use the MP4 container so adhere to the same spe
by Youden 6y ago
I don't think that's quite accurate.
There's no functional difference between a .m4b file and a .m4a file. Both use the MP4 container so adhere to the same specification, so support all the same features (including bookmarks). FFmpeg even uses the same muxer and demuxer for both "formats".
The only difference is a non-standard convention used by certain software (like iTunes) to write autiobook-related metadata only to MP4 files that use the .m4b file extension.
You'll get exactly the same result if you just change the file extension after remuxing/transcoding.
- danudey 6y agoWell, it's also worth noting that different file extensions can have different associations, so .m4b is more likely to open in an app that the user wants to use for audiobooks, rather than opening in a generic mp4 audio playing app. Even iTunes, I think, would treat files differently between m4r (Ringtone) and m4a (audio) files, so despite there being no difference at all, using the 'correct' extension might be quite a bit more convenient in the long run.
- Youden 6y agoThis is true and I'm not saying you shouldn't use the .m4b extension, I just want to make it clear that that's the only difference. A ".m4b file" is just an MP4 with a funny file extension.
- encom 6y ago>Even iTunes, I think, would treat files differently[...] Yes, because it's Apple (of course) who started using non-standard .m4a, .m4b and .m4r extensions, instead of the standard .mp4.
- LocalH 6y agoI don’t see a problem with .m4a and .m4v for standalone streams of AAC and AVC respectively.
- apetresc 6y agoWait, so an m4b stores playback position in the file itself? As in, the checksum will change and file syncers like Syncthing will re-upload every time I hit pause?
- pwinnski 6y agoaudiobook-related metadata does not include the current play position, in this case. It includes things like author and editor and narrator.
- encom 6y agoNo, that's entirely player-specific and has nothing to do with the MP4 format at all.
- majewsky 6y agoI don't know Syncthing internals, but state of the art in file syncing is to use rolling checksums to identify which parts of the file have changed. If only a few bytes of the file are overwritten, only the immediate vicinity of these bytes would be synced.