Advice for encoding target bitrate?

2011-02-07 03:01:47

I want to take my FLAC and transcode to AAC. There are around 14,399 FLAC that take  383.3 GB of space up. I'd like to fit it all on a 64GB flash drive. What target bitrate using NeroAACEnc should I use to achieve this? 128? 160? I am fairly certain 190 is to high. Should I use ABR or VBR?

Thanks

Advice for encoding target bitrate?

Reply #1 – 2011-02-07 03:07:15

What's 17% of the average bitrate of your combined FLAC files?

C.

eg. if the AVG bitrate of your FLAC files = 753kbps then you'd need AAC ABR 128kbps.

Advice for encoding target bitrate?

Reply #2 – 2011-03-05 19:47:18

I'd suggest using quicktime aac to compress your musc

Right now I have 6,400 something songs, taking up 25GB *Although there's music like on mixtapes which you cannot get flac for, so i find v2 lame rips of*

They produce very efficient and small files, and utilize smart techniques, and have been perceived by others hear to be parallel sounding with lossless

http://www.hydrogenaudio.org/forums/index....showtopic=78072

You don't have to take my word though, the easy thing would be to go in foobar, use nero aac and convert all the songs, starting from the v2 equivalent setting, and just see the total amount of space it takes up, then keep going down 2 notches until you find them fitting on 64GB or lower.

Advice for encoding target bitrate?

Reply #3 – 2011-03-06 13:40:27

Are you suggesting that “the easy thing” is to convert the entire 383.3 GB of files before checking whether the resulting files fit into 64 GB of space? And then, if the set is too large or too far below 64 GB, to delete it and start again at a different bitrate? That is, of course, completely ludicrous.

Of course, it could just be that I never woke up properly; if foobar2000 provides a predicted bitrate, maybe that’s what you’re talking about. Apologies if so! But my last sentence below would still apply.

The logical thing to do is to determine the appropriate bitrate using some simple mathematics, as carpman suggested. One could also base the calculation on total duration rather than average bitrate, but my brain is too fuzzy to suggest how right now.  However, one would have to use ABR/CBR for the result to be predictable.

Advice for encoding target bitrate?

Reply #4 – 2011-03-06 15:27:09

You coulde always use an abr-type approach.

Encode 10% of your files at some encoder setting. If the files are larger than 10% of the necessary size then lower the quality setting. Then do the same after 20%, 30% etc. You should quickly home in on an appropriate setting.

Advice for encoding target bitrate?

Reply #5 – 2011-03-06 18:00:56

Since you have an absolute storage space requirement, I'd go with CBR to make sure that everything will fit the first time...and with 14K+ files, I know for damn sure *I'd* only want to do it once.

Are all the FLACs already in fb2k's library?  Even if they aren't, just drop the entire library into fb2k, let it build the playlist, and then select all and see what the total playing time is in the status bar.

Take the formatted capacity of the flash drive (probably around 60 GB) and start doing the math until you get down to kbps - Bob's your uncle, and that's your bitrate.

For instance, here is a handy little bitrate calculator.  You have to work "backwards", i.e. enter in the total playtime and then keep tweaking the bitrate until you get to your ~60 GB or so, but at least it does all the math for you.  I tried with my 8400 song library (almost exactly 30 days - 720 hours - of playing time), and 190 kbps gave a total size of almost exactly 60 GB.  So, you're probably looking at somewhere in the neighborhood of 100-110 kbps, but give it a shot and see what it comes out to (NeroAacEnc will allow both CBR and ABR bitrates to be specified in single-digit increments).

Advice for encoding target bitrate?

Reply #6 – 2011-03-06 19:15:19

if you have time for one encode - better use CBR/ABR

if you have very much time- just encode multiple times full set of aac files in vbr

if you have time for 2-3 (or X) encodes:
- split your archive into 16 sets, each set is 24gb (=384gb/16) flac files, with each set of flac files do this:
1) encode 24 gb flac files with 2-3 different setting into 2-3 sets of aac files
2) from resulted 2-3 sets of aac files choose closest to target size (3,75 gb=60gb/16)
3) if previous encodes resulted in oversize or undersize aac files, you decrease or increase target size in next comparison
4) for calcutation of (next comparison) set target size use this: ((remaining flash space)/(remaining number of sets))

this method is good because: vbr gives you better quality, you can reach target size with good accuracy, you know remaining time and progress, you can speed up or slow down process (increase/decrease number of tries for next sets), you dont need much free space, you can program it in shell or batch files; you can use different encoders for sets (and compare their quality)

Variation of this method: after 2-3 encode of 24 gb flac set you can try to combine aac files with different settings to achive very close to 3,75 gb target size for aac set. This variation needs more time and manual work, probably not worth it, but you can use this method for last set to get closer to exact 60 gb (or you can run more vbr tries on last set).