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How to Create the Ultimate Lossy Library, High-Quality Lossy Audio Encoding Questions (and Hopefully Answers!
heyo_speaker
post Oct 10 2011, 07:52
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Hi! Every couple of years I find myself at hydrogenaudio trying to figure out what is the current best lossy audio format and the best encoder for it. I am not well-educated about the technical aspects of ripping and converting, audio quality and technology, etc., just the basic concepts involved, and it's always a struggle for me to get my head around the articles and forum posts here. This time around, I decided to post here and see if anyone would be generous enough to provide some guidance.

My goal has always been to produce not necessarily the very highest quality lossy copies of my songs, but almost the very highest -- to try to find a nice balance between file size and audio quality that leans more toward quality.

I would like to summarize my understanding of things thus far... It will be a little rambling, but don't worry, I have a summary/clarification of my questions at the end of the post.

So after my visits here a few years ago, I had concluded the following (if I remember correctly):

-- that FLAC is the best lossless audio format
-- that I should rip my CDs to FLAC for archiving, using Exact Audio Copy
-- that LAME is the best, or among the best, MP3 encoder for higher quality lossy audio
-- that I should use a LAME plug-in with foobar2000 to convert my FLAC rips to MP3s for making MP3 CDs

At the time I found a line graph here (I thought it was in the LAME article in the Knowledgebase but I can't find it now) that showed, I think, the correlation between file size and audio quality for the various LAME presets. As I remember it, as you went from lower- to higher-quality presets, quality increased at a slower rate than file size, so the gains in quality were smaller as you went from V1 to V0, for example, than when you went from V5 to V4.

I'm not 100% sure, but I think I had settled on V2 as being the best balance of file size and quality, based on that graph -- it was near to the highest-possible-quality and the gains in quality by switching to V1 or V0 seemed small compared to the gains in file size. And if I remember right, there was an option to force a constant bitrate for the best possible quality, but I didn't think the increase in file size was worth the small increase in perceived quality. But I may have later switched to V1 or V0 because I wanted to make sure I wasn't compromising too much on quality.

Later, I think I may have switched from LAME MP3 to Nero AAC when I first got my iPhone, after reading here that Nero was among the best AAC encoders, but then my computer died and I am only just now re-building my CD ripping and encoding setup after a year and a half.

I really want to make sure I use the best lossy format that is compatible with iPods and iPhones, and to use the best encoder for higher-quality audio, and I am willing to make a slight concession in quality if it makes a big difference in file size. I also prefer to set up the encoder with some good-all-around parameters to use for all of my conversions, instead of tweaking them for each album or track.

I am wondering, now that some time has passed, whether AAC has clearly surpassed LAME MP3 in terms of quality and file size at higher bitrates. I also see that a listening test was recently posted that seems to show that Nero AAC is no longer the best encoder for AAC (though the quality comparison graph was the only part I could understand!). It shows CVBR and TVBR coming out on top. I didn't know what CVBR and TVBR were, so I did a search. It appears they are associated with Quicktime AAC (perhaps certain preset bitrates?), but that's all I could figure out.

So, my questions at this point are listed below. I had intended to try to research these on my own, but I know it would take me a long time due to my lack of understanding of the things I read, and the amount of searching involved, so I decided to just put them out here and see if anyone with more experience and expertise would be willing to provide some answers, guidance, opinions, or clarification. I understand that there is some subjectivity and possibly some lack of test results to provide clear answers to all of my questions. Opinions are welcome, as well as any small thing that could help point me in the right direction.


Here they are:

-- For higher-quality lossy audio, is AAC generally considered to be better than LAME MP3 nowadays (or whatever the best MP3 encoder is) or is there still some debate as to whether LAME MP3 might be better? Or, is there a third lossy format that will work with iPods/iPhones that is considered to be better?

-- For the best lossy format, which encoder produces the best audio at the higher-quality end?

-- Is there a foobar2000 plugin version of that encoder?

-- In your opinion, what quality preset / bitrate on the high-end of the quality spectrum produces the best- or nearly the best-quality audio without an excessive sacrifice in file size? Disregarding how much space is on my iPhone; just whichever setting stands out as being the point at which anything better comes at a disproportionate cost in file size. I have decided I don't necessarily need the very highest quality setting if it comes with a major increase in file size... but if file size and perceived quality pretty much increase at the same rate, then I might just go for the very best quality. I do prefer quality over small file size, for sure, but at the same time I don't want to accept a major increase in file size for a small increase in quality if the quality is already very good by any standards. I don't have a preference as to whether it is a constant or variable bitrate; as I remember it, with LAME, the VBR presets offer more bang-for-the-buck with the quality/file size ratio.

-- Are there any other settings / parameters I should use in the encoder for a better result? Can I adjust them right in foobar2000?


And if it turns out that AAC is the format I'm looking for, and Quicktime AAC is the best encoder...


-- Is the Quicktime AAC encoder just the one that comes with iTunes? And is it also available as a foobar2000 plugin?

-- What exactly are CVBR and TVBR?

-- Which one better fits the goals I have specified? (Or is something else better?)

-- How do I specify which one I want to use in the Quicktime AAC encoder?

Any other tips or information that would help me in my quest would be very much appreciated!


I really apologize if I have written any frustrating questions in my ignorance. And I apologize for there being so many questions -- by all means, feel free to answer some while ignoring some! I ask these questions because I'm hoping to make my life easier, not to make yours harder.


My vision is to create a lossless archive of FLACs and then a lossy library, one that doesn't negate the benefits of lossyness by using extreme bitrates, or anything that is overly obsessive with quality that comes with a balloon in file size, so that I can actually carry a decent number of tracks on my iPhone. But I want to make sure that they will sound great on nice headphones and sound systems, and I don't want to cut back too much on quality when I figure iPod-type devices will have more storage space in the future.


Thank you VERY much for your time and advice!
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testyou
post Oct 10 2011, 08:28
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QUOTE
tl;dr wall of text


Both MP3 and AAC can reach transparency at higher bit rates.
You posted this in the AAC forum, so perhaps you would prefer AAC.
Preset high quality/VBR can be used with either to achieve your goal.

You might also consider using ALAC in order to play your lossless files and avoid lossy transcoding.

This post has been edited by testyou: Oct 10 2011, 08:31
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halb27
post Oct 10 2011, 09:36
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Using a lossless archive and a lossy productive collection is the usual way to go.
testyou's proposal of just using ALAC is very attractive in case you consider ALAC to play on your mobile systems.

Using FLAC for the lossless archive is one of the best choices because FLAC is rather widely supported on PC systems without having to install codec specific add-ons for a player, and because it is quite effective.
Using another codec like TAK makes sense if you're out for a better compression ratio, but difference in compression is very small usually.

As for the lossy encoding it is up to you to mark the sweet spot between quality and compression. You are into compression efficiency, and for this reason AAC has an edge over mp3 especially as it sounds like univeral usability isn't much of a concern to you. You favor Quicktime AAC which is a good choice. You can use it with iTunes or with standalone Quicktime or with the commandline tool qtaacenc. CVBR is constrained VBR which prevents the VBR mechanism from going extremely low with bitrate. As for the settings you like to use: I'd use the settings from the 96 kbps listening test as a start, take a few tracks of my music, and go up with bitrate until you're totally satisfied. As an easier way: use a setting which yields roughly 150 kbps on average for a small test set of your favorite music.

This post has been edited by halb27: Oct 10 2011, 09:45


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MichaelW
post Oct 10 2011, 11:41
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If you have an iPhone, and are not heavily into the technicalities, I guess you are using iTunes (many people hate it on Windows, sometimes for good reasons); if you are, there is a simple solution.

Keep your archive in ALAC, as people have suggested. I don't know if EAC will rip to ALAC, but you can convert FLAC files, or use iTunes to import WAVs that you have created with EAC (or DBPoweramp, which is also recommended by people who seem to know their stuff).

Connect your iPhone to iTunes. On the "Summary" page for the iDevice, you will see a checkbox labelled "Convert higher bit rate songs to 128 kbps AAC". As you might expect, this will automagically transcode your music as you sync it, and ensure you get a lot of stuff on your phone. On the puter, just play the lossless files.

Judging from recent tests, it is unlikely that you will notice any deficiency in the 128 kbps files, unless you listen to especially challenging music (truly apocalyptic metal, very synthetic synth, or harpsichords) with great attention. If you do, well, you still have the lossless files, and you can go to plan B. But it would be a shame for you to spend too much time on this, since recent tests are showing that it is becoming increasingly hard to tell one good lossy encoder from another.

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tawd
post Oct 10 2011, 12:02
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I use Foobar with Qaac to encode to Quicktime AAC for my phone and it works really well. It is the exact same file one would get with iTunes, but with out the incredibly bloated iTunes software. Conveniently, Qaac will encode to Apple Lossless as well so you can use one program to decide which iPhone compatible format you prefer.
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IgorC
post Oct 10 2011, 19:22
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QUOTE (MichaelW @ Oct 10 2011, 07:41) *
since recent tests are showing that it is becoming increasingly hard to tell one good lossy encoder from another.

The tested LC-AAC encoders were mature already for years. The quality of Nero and QuickTime LC-AAC encoders is pretty the same as for 2005-2006. Of course there were some tweaks but the main level of quality reached its optimum.

The thing is that nobody has organized the public test for LC-AAC in last 5 years.
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krafty
post Oct 10 2011, 19:47
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QUOTE
lossy productive collection


What did you mean, did you mean "only the favourite songs" ?
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halb27
post Oct 10 2011, 20:35
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By that I mean the music listened to, especially on a mobile device, in contrary to the archive which is the source for lossy encoding.
I did not think about whether the 'productive collection' consists of the entire archive or a selection. The codec consideration is independent of this question.

This post has been edited by halb27: Oct 10 2011, 20:36


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heyo_speaker
post Oct 17 2011, 08:12
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Thanks, everyone, for all the help! ALAC is a good idea -- I forgot Apple had a lossless format (obviously it's been a while since my mind was on this subject). I'm assuming it's on par with FLAC in terms of compression for you guys to recommend it. I should encode one of my albums in ALAC and see how much space it would take up on my phone. I assume I will want to go the lossy route, though, to fit more music on my phone.

If I can fit a decent amount of ALAC music on my phone, I might just use ALAC for archiving for the convenience of its compatibility with iTunes and the iPhone operating system. Otherwise, it seems I should use FLAC for maximum compatibility.

Based on your responses, it sounds like I was on the right track, that AAC is a good lossy format and Quicktime AAC is a good encoder. Or, at least, it sounds like you're suggesting that the quality differences between different lossy formats and encoders are small at higher bitrates. And it sounds like you're suggesting that the compression differences between lossless formats/encoders are small. And that the main considerations for choosing a lossless or lossy (at high bitrate) format normally are convenience and compatibility rather than quality and compression ratio. Is this a correct interpretation?

Just to clarify a few things:

Is Quicktime AAC built in to iTunes and Quicktime? Meaning that if I start up either application and go to convert some music to AAC (or "import" it, or however it's done), it will already be using the Quicktime AAC encoder, without me having to install anything special?

Would you recommend CVBR over TVBR to guarantee higher quality? Does the "T" in "TVBR" stand for "target", meaning that with TVBR you choose a target average bitrate whereas in CVBR you choose a minimum bitrate (in addition to a target bitrate)? Is CVBR just TVBR with the added ability to guarantee minimum quality (at the cost of file size increase)? I'm just using my imagination here to fill in the blanks -- sorry if I'm way off.

And halb27, thank you for all the info and advice. Are the kbps settings you recommended for my first listening tests, like, target bitrates, or are they the minimum bitrates for CVBR? (Or is 96 kbps a CVBR minimum and 150 a target average?) I suppose I could figure out some of this stuff by playing around with iTunes or Qaac once I get them installed.

Does anyone know whether the "Convert higher bit rate songs to 128 kbps AAC" option in iTunes uses CVBR, TVBR, or something else? And is 128 kbps a target bitrate or a minimum CVBR bitrate?

What is "LC-AAC"? Is it something I should know about?

So, based on the responses so far, it sounds like the recipe for finding a good balance between quality and file size is to start with a good minimum quality setting and work my way up until it sounds totally acceptable to me, or to find the highest quality (above this starting minimum) that still allows me to fit the desired amount of music on my phone. (And then possibly kick up the quality to the next level, just to be obsessive.)

The next thing I need to decide is which bitrate setting to use as my starting minimum -- which encoding method and bitrate setting do most people consider to be good? Do I go with CVBR, TVBR, or some other method? Do I start at 96 kbps, 128 kbps, or 150 kbps? I think I will be able to figure some of this out if someone can enlighten me with the answers to the questions above.

Thanks again, you guys are really helpful!
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halb27
post Oct 17 2011, 09:54
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As for the questions towards me:

a) I am always thinking in terms of 'average bitrate', and no matter the setting I'd always find out by encoding a test set of music representative of my collection. 10 to 20 tracks are sufficient to get a sufficiently precise impression.
b) If you want to experiment with settings and quality I'd start with the 96 kbps listening test settings as I said. So in the case of CVBR: '--cvbr 96 --highest --samplerate keep'.

I have no personal experience with iTunes, so can't give advice here.

Just another suggestion: I'd try to find a good way of doing things, but not try to find the 'ultimate way of creating a lossy collection' within a huge bunch of varying parameters. You have set up your framework as far as I can see (Quicktime AAC at low to moderate bitrate). So just decide upon CVBR or TVBR according to your feelings on a full or restricted allowance to choose bitrate - you won't get differentiating facts, just consider both as being equally fine. And do some tests to see at what settings you're totally satisfied with quality.

LC-AAC is what you should be interested in, kind of standard AAC. There's also HE-AAC aka AACplus, which improves quality for very low bitrate because of a much simplified way of encoding high frequencies leaving space for a better accuracy of the more important frequencies. At 96 kbps and above HE-AAC should be avoided. Also you can't play HE-AAC with every AAC playing device.

This post has been edited by halb27: Oct 17 2011, 10:07


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buklau
post Oct 18 2011, 06:51
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If I can fit a decent amount of ALAC music on my phone, I might just use ALAC for archiving for the convenience of its compatibility with iTunes and the iPhone operating system. Otherwise, it seems I should use FLAC for maximum compatibility.
Yes, FLAC is probably the most popular lossless format, however ALAC is fairly common as well. Compatibility wise, I find ALAC to be 'friendlier', at least on the systems I use. iTunes natively recognizes it, and since it's stored in the .m4a container, Windows will at least recognize it as a music file (whereas it won't natively recognize .flac). Compression wise, it is practically identical. I don't have a large library (5497 songs), but in FLAC (level 8) it takes up 150 GB, in ALAC it takes up 152 GB.

Based on your responses, it sounds like I was on the right track, that AAC is a good lossy format and Quicktime AAC is a good encoder. Or, at least, it sounds like you're suggesting that the quality differences between different lossy formats and encoders are small at higher bitrates. And it sounds like you're suggesting that the compression differences between lossless formats/encoders are small. And that the main considerations for choosing a lossless or lossy (at high bitrate) format normally are convenience and compatibility rather than quality and compression ratio. Is this a correct interpretation?
Most people have never done double-blind listening tests with their own music at different bitrates and with different codecs; with the progression of lossy codecs, you'll probably be surprised at the bitrate where the majority of your music becomes transparent (hint: 256kbps iTunes AAC CBR is probably overkill).

Is Quicktime AAC built in to iTunes and Quicktime? Meaning that if I start up either application and go to convert some music to AAC (or "import" it, or however it's done), it will already be using the Quicktime AAC encoder, without me having to install anything special?
It's built into iTunes on all platforms. You can configure the quality under 'Import Settings', and convert tracks by right clicking and selecting 'Create AAC version'. Keep in mind iTunes can only convert formats it recognizes (you can't add FLAC files to your library and expect it to be able to convert them to ALAC or AAC).

Would you recommend CVBR over TVBR to guarantee higher quality? Does the "T" in "TVBR" stand for "target", meaning that with TVBR you choose a target average bitrate whereas in CVBR you choose a minimum bitrate (in addition to a target bitrate)? Is CVBR just TVBR with the added ability to guarantee minimum quality (at the cost of file size increase)? I'm just using my imagination here to fill in the blanks -- sorry if I'm way off.
CVBR is an Apple (iTunes) AAC phenomenon and it stands for Constrained VBR. It is necessary (for iTunes) if you plan to use HE encoding (typically ~64kbps). TVBR stands for True VBR and is somewhat difficult to actually get iTunes to do (if you select 'use VBR' in iTunes, it will use Constrained VBR regardless of format, you have to do something special to get True VBR). The most recent listening test at ~96kbps suggests no statistical significance between the quality of CVBR and TVBR, (at least at that bitrate) - http://listening-tests.hydrogenaudio.org/i...-a/results.html

Does anyone know whether the "Convert higher bit rate songs to 128 kbps AAC" option in iTunes uses CVBR, TVBR, or something else? And is 128 kbps a target bitrate or a minimum CVBR bitrate?
See above, it will always use CVBR unless you do a special procedure.

What is "LC-AAC"? Is it something I should know about?
Low complexity AAC, standard AAC without the bells and whistles of things like HE AAC, or HE AAC v2 which uses SBR (note, the fancy things are used to make decent sounding lossy files at very low bitrates, not something that is intrinsically 'better' than LC-AAC; for example, some encoders will only allow you to enable HE AAC once you select a bitrate sub ~84kbps).

The next thing I need to decide is which bitrate setting to use as my starting minimum -- which encoding method and bitrate setting do most people consider to be good? Do I go with CVBR, TVBR, or some other method? Do I start at 96 kbps, 128 kbps, or 150 kbps?
It's probably better to get True VBR if you can (again, CVBR vs. TVBR is only an issue for Apple AAC), and the best advice I can give is do whatever sounds best to you. I personally find most music to be transparent at ~150kbps Nero AAC VBR, however I encode my music to 64kbps Apple HE AAC CVBR to fit it on my phone (sounds fine through the tin buds I have).

This post has been edited by buklau: Oct 18 2011, 06:59
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