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Topic: Audiobook base format ogg, opus, or aac/m4b (Read 3544 times) previous topic - next topic
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Audiobook base format ogg, opus, or aac/m4b

Situation: I have a bunch of 64-kbps AAC audiobooks that I had to edit a bit, so they are all currently in FLAC format.

Quandry: These files are way too big and no reason to keep them as FLACs that I can see.  Was thinking of going to Opus as a base format since they come from a lossy format.  (I know I've lost a bit in conversion, but editing was necessary.)  If so, is 48 kbps adequate to encompass audiobooks with background music as well as the need for possible temporary conversion to other formats (due to incompatibility with players and apps)?  Or is 64 kbps better e.g., to compensate for conversions and maintain as much integrity as possible?  Or is AAC/M4B or Ogg better as a base format?  (I mostly use Android, but others in my family use iPhones.)

Related: I've looked through the info on the Opus wiki and other posts on the topic.  Seems like Opus is really great (performance, size, open source, etc.).  There still isn't that much support for it, but it's really only been a couple years and seems to be steadily gaining wider acceptance, e.g., like native support in Android 5 possibly.  Is that perception of growth correct--curious because I'm wondering if it seems like it's gonna be around for a while.

I've read a bunch from this forum over the last few years, but am still a bit muddled. Thanks for the recommendations!

Audiobook base format ogg, opus, or aac/m4b

Reply #1 –
I think you are going to have to answer this for yourself...  You'll have to decide if the quality is good enough, and if the format is acceptable...

Quote
I know I've lost a bit in conversion, but editing was necessary.
You haven't actually lost anything yet.  The damage is done during lossy compression.  If you re-save to a lossy format, then you are going through a 2nd lossy compression step.

I'd probably stick with 64kbs AAC.    AAC was designed for minimal additional damage with multiple encode/decode cycles.    If you convert to another format (or a lower bitrate), those choices probably will be worse.

Nobody can predict the future...  Currently almost every portable player can play AAC & MP3, so these are probably the "safest" lossy formats.    FLAC (and ALAC) is lossless, so if it goes "out of style" you can convert to another lossless format in the future.    And, if you keep FLAC/ALAC as your master archive, you can convert to any lossy format in the future with only one additional generation of lossy encoding.

Audiobook base format ogg, opus, or aac/m4b

Reply #2 –
I haven't tried it, but a couple of programs claim to be able to edit AAC losslessly (i.e. bitstream editing, without re-encoding). Don't know how well it works. It could be hopeless.

Cheers,
David.

Audiobook base format ogg, opus, or aac/m4b

Reply #3 –
Thanks for the info and recommendations guys!  I'll probably stick with AAC for now then and check out those AAC edit tools for future editing.

Audiobook base format ogg, opus, or aac/m4b

Reply #4 –
Opus is going to be around for a while.  The main question is whether you consider it to have arrived yet  There is good support in some areas (eg. the main web browsers), not so good in others (eg. portable music players).  It is well suited for speech, with 24-32 kbps per channel giving very good quality.  Encode some and listen, then decide which level is good enough for you.  At 64 kbps (for stereo) you can certainly hear some minor imperfections with music, but I find speech to be very clear at that level and even lower.

P.S.  Probably need to stop calling Vorbis files Ogg now.  Opus and Vorbis both (usually) come in Ogg containers.  If you're concerned that they might be in a different container then you might say Ogg Vorbis.  People don't seem to say Ogg Opus, but maybe it will become more common when Opus shows up in other containers.