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[Dave T]

I have a library of about 19,000 songs, taking up about 150 gig (!).  The files are all MP3 encoded - about 1/3 at VBR Highest Quality, and the rest at 320KBPS.   I know the 320kbps files are killing me - a friend encoded those, and he likes that bit rate for some reason.

I'm giving my wife a 60 gig IPod for Xmas, and would like to fit as much as possible onto it.  This will mean transcoding my files down to a more reasonable bitrate to fit on the IPod.

So, can someone please point me to some stats on the compression ratios of the different bitrates that MC can transcode to?  I'm thinking some kind of VBR encoding.  Since it's so many files, I'd rather not do this via trial and error - it would take forever.  I also need to know what the average file size is for a music file.  Since I don't know the exact mix of my library - I'm not sure what my average compression ratio is.

I'd also like some subjective opinions on the sound quality of the different bitrates.  I don't think it will matter overly much for listening thru the headphones on the IPod, but we'll also be hooking it up to a stereo, where overly compressed music might be more noticable.

Thanks!

- Dave

[hit_ny]

I'm giving my wife a 60 gig IPod for Xmas, and would like to fit as much as possible onto it.  This will mean transcoding my files down to a more reasonable bitrate to fit on the IPod.

Why do you want to re-encode from mp3 (lossy, so now dbl the loss) when the originals have been ripped at a pretty good rate ?

You can already fit nearly a third of your entire library on that 60GB iPod. That's nearly 600 albums in the palm of your hand. If you have been rating your collection, pick the best ones.

I usually encode using lame aps, gives a good compromise between size & quality. My music works fine with those settings, your's may not. in which case you want alt preset extreme. But this is for ripping new albums unless you can re-rip the earlier ones.

[Dave T]

Thanks, hit_ny.  I don't really want to debate why I want to do what I want to do, but - I'm not talking about transcoding my library that's on the computer, I want to make a copy of it to put on the IPod.  And, although I could fit a ton of songs onto the IPod already, I don't want to go through the excercise of having to decide which 1/3 of what I have makes the cut and gets put on the IPod.   Plus, there's the cool factor of having my whole collection available for travel.

So, that's my explanation, but I'm really just looking for the answer to my question.  So, do you (or does anyone else), know what the compression ratios are for the various bit rates (and codecs) that I can put on the IPod?

Thanks.

- Dave

[hit_ny]

I'm not talking about transcoding my library that's on the computer, I want to make a copy of it to put on the IPod.

How do you do this without a transcode ?

It sounds like you want to stuff your whole library into the iPod. You are not too bothered about sound quality so long as its bearable.

150GB ---->squeezed into 60GB iPod or a reduction by a factor of 2.5

How about 128k (same reduction compared to your 320k) as your encoding setting. You could use ABR as this will give a predictable size with slightly higher quality than CBR.

128k should sound ok over headphones and average over speakers. That is if you encode from source, it will sound slightly less good with a re-encode. Only you can be the judge of this. If you listen in a car, the surrounding noise would mask this anyway.

EDIT...Changed vbr to abr.

[edbro]

Pardon me for jumping in here but I have a related question. I have a Sandisk MP3 player that can't accept a bitrate higher than 128K. What is my best encoding option? I've been using CBR128 but can I use VBR and tell it not to exceed 128? If so, how do I set that 128 limit? Hit_ny's comment to that effect got me thinking about it.

[Dave T]

How do you do this without a transcode ?

It sounds like you want to stuff your whole library into the iPod. You are not too bothered about sound quality so long as its bearable.

150GB ---->squeezed into 60GB iPod or a reduction by a factor of 2.5

How about 128k (same reduction compared to your 320k) as your encoding setting. You could use ABR as this will give a predictable size with slightly higher quality than CBR.

128k should sound ok over headphones and average over speakers. That is if you encode from source, it will sound slightly less good with a re-encode. Only you can be the judge of this. If you listen in a car, the surrounding noise would mask this anyway.

EDIT...Changed vbr to abr.

Sorry - I guess I'm being confusing.  I ~am~ going to transcode the library on the computer, but I'm going to do it to a seperate location.  Making a copy of the library encoded at a lower bitrate.  So I'll copy the library and then put the copy on the IPod.  But I'll keep the high bitrate version for normal use.

And, I do care about sound quality.  But I'm willing to compress it a lot more than it's compressed now.  I don't want to compress it so far that it starts sounding bad on the IPod, though.

So - back to my question - what I'm really looking for is a table of the compression rates of the different bitrates.  That must be available.  Maybe I should get off my butt and try to find it myself by googling.  I thought it would be a well known thing here, but maybe not.  And - what's "ABR"?  I know VBR and CBR, but ABR...?

Thanks.

- Dave

[Alex B]

For Mp3 files I would recommend the latest encoder (check for updates in MC) and this custom setting:

-V 4 --vbr-new   ~154 kbps

or if you must have a lower bitrate:

-V 5 --vbr-new   ~134 kbps
-V 6 --vbr-new   ~121 kbps

The bitrate estimates are from my test here: http://www.hydrogenaudio.org/forums/index.php?s=08b46279a25d8b11e76aef72959130ba&showtopic=37011&st=50&p=328558&#entry328558.
Classical music averages often a bit lower, but that depends greatly on the source material. Genres like heavy metal, electronic, techno etc. produce usually higher bitrates.

One hour of music at
154 kbps needs 69,300,000 bytes = about 66.1 MB of HD space
134 kbps needs 60,300,000 bytes = about 57.5 MB of HD space
121 kbps needs 54,450,000 bytes = about 51.9 MB of HD space

When you are starting from an already lossy file the result will be worse than encoding directly from a lossless source at the same setting. That is why I would not recommend using any lower settings than these when transcoding MP3 files to lower bitrate MP3 files. Also, I would transcode only files that are over 192 kbps.

If you absolutely must make them smaller you could try ABR instead. It is VBR too, but the bitrate is restricted to a certain average value and thus more predictable. For example: --preset 115 would make about 115 kbps files. One hour of music at 115 kbps needs 51,750,000 bytes = about 49.4 MB of HD space.
 
Actually, I think iTunes AAC might be a better format for transcoding at 128 kbps or lower. If your original files are in MP3 format you could try iTunes for making AAC files. The newest iTunes has also a VBR mode for AAC and that would probably be the best AAC option. After the files are converted you can use MC for handling the iPod.

[Dave T]

In the interest of getting something going on this, I started my transcode using 128 ABR.  I can always re-do it, but I want to have something to put on the IPod.  So you think AAC 128 would be better?  Can MC transcode to AAC?  I didn't think ITunes could transcode.

In any case, I started it last night, and it's been running for about 12 hours.  It's roughly 1/10 done (!).  At this rate, it's going to take 5 days!!  Is there any way to do faster transcoding?

Thanks again.

- Dave

[GHammer]

Using the commandline version of whatever encoder may be faster. But you have the need to decode first most likely.

If you were going from and to MP3 LAME may be faster from the commandline.

You'd have to experiment.

But from MP3 to AAC? I think you will have to use some sort of frontend whether MC, foobar, or some other. And it will be somewhat slower.

[hit_ny]

I'm under the impresion that 128k AAC and 128k ABR are very similar.

[Alex B]

LAME MP3 transcoded to LAME MP3 can produce extra artifacts because of some frame boundary issues. When the target format is different those issues don't exist.

iTunes has currently the best VBR AAC encoder and it is probably better than LAME VBR at low bitrates. MC doesn't have an AAC encoder, but iTunes can convert MP3 files directly to AAC.

Gogo, Helix and WMP10's FhG (with a third party command line frontend) would be faster MP3 encoders (and a bit lower quality). I don't have time to explain their usage now, but they can be used as external encoders with MC. A search at hydrogenaudio.org would probably find more information about these MP3 encoders.

[Alex B]

Actually, I don't know if the frame boundary issue happens with the decoder used in MC, but in general MP3 to MP3 encoding is not considered to be a good combination.

In this HA thread transcoding from various formats to LAME MP3 was tested and discussed: http://www.hydrogenaudio.org/forums/index.php?showtopic=32440. MP3 to MP3 was the worst. Also, the frame boundary issue was mentioned. Transcoding MP3 to other formats was not tried in that test.

[Dave T]

Ok, I restarted the transcode job using ITunes at 128K VBR.  It's much faster - about 3 times as fast (!).  The compression doesn't appear to be quite what I had hoped.  At this rate, I think I'll barely be able to fit all the music on the IPod, but with nothing to spare.  I'll probably go in and selectively delete some music to make more room.  Thanks for all the advice!

Still would like to see a table showing the different compression ratios for the different bit rates.  That must be out there somewhere, but I haven't been able to find one.

[Alex B]

The compression ratio is directly relative to the average bitrate.

The original 16-bit 44.1 kHz wave file is always 1411 kbps => 1:1

141 kbps => 10.0:1 (10.0%)

320 kbps =>  4.4:1 (22.7%)
256 kbps =>  5.5:1 (18.1%)
224 kbps =>  6.3:1 (15.9%)
192 kbps =>  7.3:1 (13.6%)
160 kbps =>  8.8:1 (11.3%)
128 kbps => 11.0:1 ( 9.1%)
112 kbps => 12.6:1 ( 7.9%)
 96 kbps => 14.7:1 ( 6.8%)

and so on.

[Tab]

Hi

I'd make a copy of one track at different vbrs and compare them for size and sound. I'm not sure how else you'd get just what you want, unless you make further compromises. Restricting bit rate variation wont help the quality/size balance.

Tab

[Dave T]

Ugh.  I've been away all week, and started the transcode process before I left.  Unfortunately, the resulting library is much larger than I'd estimated.  I thought it would be a bit more than would fit on the IPod, but not this much.  So, I'm faced with the task of manually removing about 2000 songs to make it fit on the IPod, or recompressing.  I'm inclined to take the easy route and re-compress to a lower bitrate.  Can anyone who's compared tell me how much worse AAC at 96kbps would be than 128kbps?  96 would fit easily.  128 is what I have now.

Also, the 128kbps AAC files that ITunes produced won't play in MC.  They'll play in ITunes, but when MC plays them, I just get silence.  Has anyone seen this?

- Dave

[hit_ny]

..does your library stay static or will it increase in size over time ?

Even if you manage to shoehorn your current library into the iPod, what happens when you get more and there is no more space left on the iPod ?

...get another

[Alex B]

Ugh.  I've been away all week, and started the transcode process before I left.  Unfortunately, the resulting library is much larger than I'd estimated.  I thought it would be a bit more than would fit on the IPod, but not this much.  So, I'm faced with the task of manually removing about 2000 songs to make it fit on the IPod, or recompressing.  I'm inclined to take the easy route and re-compress to a lower bitrate.  Can anyone who's compared tell me how much worse AAC at 96kbps would be than 128kbps?  96 would fit easily.  128 is what I have now.

iTunes AAC 96 VBR is quite good when encoding directly from a lossless source, but I don't know what happens when the source is a lossy MP3 file. There is also the 112 VBR option.

I think you just have to trust your own ears. Select files of various genres and MP3 VBR bitrates and make some test encodings. The VBR MP3 files that have the highest average bitrates are probably more difficult to encode.

Also, the 128kbps AAC files that ITunes produced won't play in MC.  They'll play in ITunes, but when MC plays them, I just get silence.  Has anyone seen this?

Check this thread out: http://yabb.jriver.com/interact/index.php?topic=30561.0.

[Dave T]

Ok, I'll try the 96, and hope for the best.  I'm not really up for doing an A/B comparison - I'm too lazy.  Plus, my main system is very revealing, so even if I could tell the difference there, that doesn't mean I'd notice it on whatever I listen to with the IPod.  Or, do I just test on the IPod?  But then if I hook the IPod up to a nice amp and speakers, imperfections might start showing up.  That's why I'm interested in hearing others' subjective opinions.

Regarding the silence with the AAC - I skimmed through that thread.  Yikes!  Sounds like it's a bit of a project to solve this one.  I do have QT and ITunes installed on the computer.  I didn't install ffdshow (isn't that just for video playback?).  Maybe at some point I'll take the time to get this working.  I was hoping it was a simple fix.

[Alex B]

Regarding the silence with the AAC - I skimmed through that thread. Yikes! Sounds like it's a bit of a project to solve this one. I do have QT and ITunes installed on the computer. I didn't install ffdshow (isn't that just for video playback?). Maybe at some point I'll take the time to get this working. I was hoping it was a simple fix.

Yaobing (from JRiver),

What is the last word on this? What would you recommend?

I can play AAC files without problems, but I have so many codecs installed that I really don't know what to recommend.

[Yaobing]

Regarding the silence with the AAC - I skimmed through that thread.  Yikes!  Sounds like it's a bit of a project to solve this one.  I do have QT and ITunes installed on the computer.  I didn't install ffdshow (isn't that just for video playback?).  Maybe at some point I'll take the time to get this working.  I was hoping it was a simple fix.

If you have QuickTime installed, MC should play the file.

What is the extension of your aac file (m4a, m4p, or aac)? If it is DRM protected, MC will have to play it using QuickTime (which is the case if the file extension is m4p). m4a files are played using native playback engine if needed filters are present (see below). If the filters are not present, MC uses QT (if present) to play. We also attempt to play files with aac extension the same way as m4a. However we recently have one user having problems with aac extension possibly because the files were encoded using AACPlus in WinAmp. It appears that AACPlus format can be decoded by 3ivx decoder only if it is in an mp4 container. I would guess that iTunes would always use mp4 contained format, right or wrong?

Yaobing (from JRiver),

What is the last word on this? What would you recommend?

I can play AAC files without problems, but I have so many codecs installed that I really don't know what to recommend.

It seems that the only sure thing is 3ivx filters. FFDShow would work if you have Media Splitter to go with it (e.g. Haali Media Splitter).

[Dave T]

Yaobing:

Thanks for the reply.

The file extensions are m4a.  I do have Quicktime installed.  But, I get silence when I try to play the m4a files.  So, I guess I need to install the 3ivx filter(s)?  How do I do that?

- Dave

[Yaobing]

Yaobing:

Thanks for the reply.

The file extensions are m4a.  I do have Quicktime installed.  But, I get silence when I try to play the m4a files.  So, I guess I need to install the 3ivx filter(s)?  How do I do that?

- Dave

It can be downloaded from here:
http://www.3ivx.com/download/windows.html

Run downloaded executable to install.

[Dave T]

Thanks, that worked!!

And, my 96kbps AAC transcode finally finished, and it did finally all fit on the IPod. 

[hit_ny]

..And what are your thoughts regarding the (ahem) sound quality ?

[Dave T]

I haven't listened to it other than to verify that it was working before giving it to my wife (the IPod was a Christmas gift for her).  The sound sounded reasonable, but I'll listen to it more carefully sometime.   You sound skeptical that the sound would be acceptable.  Is that from personal experience?

I'm pretty happy that I was able to fit all the music on there.  I tried to go through the process of figuring out what to put on there, but it became an odious task.   I'd have to take out thousands of songs to make any signifigant dent in the size needed, and I couldn't think of any way to go through the music and exclude certain tracks that wouldn't have taken days to do.  All the music I have is stuff that I'd conceivably like to listen to at some point, or I wouldn't have it in the first place.  And when you have a 60 gig IPod, it's not like you're only putting your favorite, frequently listened to stuff on it either.

- Dave

[hit_ny]

I haven't listened to it other than to verify that it was working before giving it to my wife (the IPod was a Christmas gift for her).  The sound sounded reasonable, but I'll listen to it more carefully sometime.   You sound skeptical that the sound would be acceptable.  Is that from personal experience?

At the rate you re-ripped at, they should sound ok (?) with the cheap white buds apple gives you or via a casette adapter in a car or even computer speakers.

Connected to a stereo, is iffier. The more expenisve the equipment you connect the iPod to, the more the imperfections will stand out.

But that's the subjective thing about it.

Also she will have seen you put in a lot of hard work into this project. I'm told this is the really important part, moreso than the result

You're fine