Advice pls re: converting to HE AAC v2

[ahavvas]

After reading forums, mainly at Hydrogenaudio, I have finally settled on dBpoweramp mainly because I have decided on AAC format and dBp easily allows me to use the Nero 7 AAC codec which I felt is well rated (?)

In a nutshell, I would like some advice about whether to convert AAC files once they are stored on my PC. (Now I am writing this, my question seems to have become a lot more complicated, and I find I now need some help planning my ripping and format use).

I have a Nokia N82 with 8GB flash memory and want to keep all my music on there rather than keep downloading or synching to it.

To do this I have been thinking about compressing to 64 kbps but as the phone can play HE AAC v2 (or eAAC+ as Nokia refers to it) I feel happy with the quality considering it is on a mobile player.

However, I want better quality on my laptop where I will be ripping the CDs to.

So my main question is: should I rip my CD's once to my PC at a higher quality (probably to AAC LC at about 150 kbps) and THEN convert them to 64 kbps (probably HE AAC v2) --- OR --- should i re-rip again for purposes of putting music on my phone to avoid converting an already compressed file ? (The point being, I'm not sure how much "degradation" I can expect by converting the files I would have ripped to my PC).

The other questions which arise from this are:

* if I convert files to the phone, are there any "issues" i.e. will the benefits of HE AAC v2 be "preserved" and will the files work on my phone properly compared to if I had just ripped them to the desired format ??

* I understand HE AAC v2 uses PS, quoted as kicking in at 48 kbps and below - so I wonder whether it would be better to go even lower than 64 kbps to get the "benefit" of PS ? Will I notice PS ?

* ref point above, does the force HE AAC v2 option in dBpoweramp CD ripper make PS kick in at bit rates above 48 ??

* am I silly to bother ripping to AAC LC at 150 kbps when I could just buy more hard disk space and rip to lossless ? (I only have about 30 GB spare on the laptop and didn't want to muck around adding storage although I realise it is probably easy to add an external drive to the wireless router)

* am I silly to want to use 48 - 64 kbps on the mobile music player using HE AAC and are there any other options/considerations ?

I appreciate this has turned in to a bit of a crappy blog post from a first-time newbie but I have spent weeks on forums here, winamp and at hydrogenaudio, and I still have these last unanswered questions.

Any support or advice would be very much appreciated - and if it helps, I do really like the dBpoweramp ripper and converter programme, and am looking forward to being able to ditch Winamp player to try out dBpoweramp (which I understand isn't presently compatible with DB12 (?)

[xoas]

Re: Advice pls re: converting to HE AAC v2

I haven't worked a lot with HE AAC but I can offer up what might be some helpful thoughts regarding a few of the issues you raise her.

should I rip my CD's once to my PC at a higher quality (probably to AAC LC at about 150 kbps) and THEN convert them to 64 kbps (probably HE AAC v2) --- OR --- should i re-rip again for purposes of putting music on my phone to avoid converting an already compressed file ?

Standard wisdom says you are better off ripping once for the PC and once for the phone since you lose some audio quality converting to lossless in the first place. So if a CD is converted to HE AAC at 64 mbs this should sound better than if youo convert the same CD to AAC LC at 150 kbs and converted from there to HE AAC at 64 mbs. And standard wisdom is absolutely correct in that more of the original audio information will be lost through the intermediate conversion and you may also invite a certain degree of further degradation in audio quality than if you converted directly from CD to a lower bitrate.

Having said this, there are many cases in which the end difference is not audible to the listener. In that case, the convenience of not ripping twice may outweigh an imperceivable loss of audio quality. The only way to make sure of this would be to prepare a range of tracks representative of the full audio range of the music you intend to store and play on your Nokia and to convert them both directly to the lower bitrate and converting them through the 2-stage process. Listen to and compare the tracks and see if you notice a difference. (Ideally you would do a blind ABX test but this involves some extra effort). If you want to maximize the chances of finding a difference, listen to and compare the tracks through your stereo (if you have hooked your computer to your stereo) or through your highest quality playback source (probably your computer, especially if you have decent speakers and a decent sound card). But since a difference you can hear on your stereo may still be imperceptible on your Nokia, the more practical test would be to compare them over the Nokia.

am I silly to bother ripping to AAC LC at 150 kbps when I could just buy more hard disk space and rip to lossless ? (I only have about 30 GB spare on the laptop and didn't want to muck around adding storage although I realise it is probably easy to add an external drive to the wireless router)

Again there are 2 schools of thought. Quality-wise lossless always wins out and you have a variety of storage options including burning the lossless tracks to CD for archival purposes, storing the lossless files on an external drive or ading more hard drive space to your system. Lossless should provide superior audio quality on playback and it gives you a copy you can work with if you want to reconvert for another purpose (like converting to a low bitrate lossy format for your Nokia or for some other player).

But there are many of us who opt for storing in a lossy format to ease the storage situation. For many of us the key is to locate the lowest bitrate within our format that sounds the same to us as a listener as the original CD (this represents the point of transparency, which is what you ideally hope for). Again, determining the point of transparency requires a bit of trial and error (or a lot of trial and error depending upon how persnickety you want to be and how many different formats you want to consider).

The other topic I can speak to is that while dBpowerAMP Audio Player (or dAP) is not compatible with dMC r12, you can still use it and it is free. You do need to install it to a different folder than the one in which you have dMC r12+ and you need to install a different set of codecs for the formats you plan to listen to (you need to use the Legacy codecs from Legacy Codec Central). If you do give dAP a try, I strongly suggest that you try the r3 beta6 version that is available from the beta section of the forum. This is more stable and performs better than the r2 standard version available from the Products page. But do visit the Products page to review the compatibility notes.

Good luck and best wishes,
Bill

[ahavvas]

Re: Advice pls re: converting to HE AAC v2

Can I assume that converting from lossless to lossy is "acceptable" i.e. much better than converting from lossy.

Also, is there anyway to rip from CD once and encode to two different and seperate files ? (that could be a very dippy question but thought I'd ask).

[LtData]

Re: Advice pls re: converting to HE AAC v2

Yes, lossless to lossy is better than lossy to lossy.

Use the Multi-Encoder for dMC to encode to 2 formats at once.

[ahavvas]

Re: Advice pls re: converting to HE AAC v2

Thanks

Lastly, I would be grateful if someone could point me to a comprehensive guide to AAC HE v1 and v2. I have searched all over web, here and Hydrogenaudio but can't find the info I am looking for. In particular:

* At 64 kbps, is HE v1 or v2 "better"
* Does Parametric Stereo actually come in to play at 64 kbps and if it does, is it better to have it at this bitrate
* Do I need to use the force option in Music Convertor encode tab option or will the Nero encoder use the most suitable (LC, HE v1 or HE v2)
* are there any up to date listening tests covering AAC HE at low bitrates ?
* generally, any other detailed info about the pros and cons of using AAC at 64 kbps so I can trade some quality to achieve my whole CD colection on my 8 GB portable device

[LtData]

Re: Advice pls re: converting to HE AAC v2

It looks like the Wikipedia pave for HE-AAC answered some of your questiosn: http://en.wikipedia.org/wiki/HE-AAC

As for Nero, I believe if you don't force a profile, it automatically picks the best profile (LC, HE AAC, HE AAC v2) based on the bitrate.

[ahavvas]

Re: Advice pls re: converting to HE AAC v2

Thanks - I did review the Wikipedia article a while ago and followed most of the links. I guess what I was hoping for was some guide or advice from one of the knowledgeable kind of people viewing these and similar forums who have some (or preferably quite a lot) of knowledge and experience of using these AAC formats at around 64 kbps.

From the Wikipedia article and elsewhere, it seems that HE-AAC v2 is appropriate for 48 kbps, possibly (?) as PS kicks in there [quote from Wikipedia: Scientific testing by the European Broadcasting Union has indicated that HE-AAC at 48 kb/s was ranked as "Excellent" quality using the MUSHRA scale. [1]. MP3 in the same testing received a score less than half that of HE-AAC and was ranked "Poor" using the MUSHRA scale].

On the other hand, [further quote from Wikipedia article: Other testing indicates that material decoded from 64 kb/s HE-AAC does not yet have similar audio quality to material decoded from MP3 at 128 kb/s using high quality encoders]

Again, I am still confused about the paradox (that I am probably imagining) that 48 kbps using HE AAC v2 could sound better than HE AAC v1 at 64 kbs. I appreciate that based on some peoples standards neither of these would be acceptable and know they probably wouldn't rate against Mp3 at 128 kbps, but as I am listening on the move, the compression is more important.

Thanks for dialogue so far, and thanks in advance for any further comment, especially if you can answer the point above, or have any experience of using these formats.

[JulianL]

Re: Advice pls re: converting to HE AAC v2

Hello ahavvas. I hope you might still be subscribed to this thread.

How far did you get with answering your questions? I just found this thread and you are asking exactly the same questions as I have regarding what format to use for your mobile device. I never had your lossy -> lossy vs lossless -> lossy issue because my master rips have always been to lossless (FLAC) format for use at home but I am now at the point where I plan to invest significant time in converting most of my FLAC library (about 500 CDs) to AAC so the AAC format to use is a huge issue for me.

I've done listening tests at 64kbs for HE-AAC v2, HE-AAC v1, Ogg Vobis, mp3 and WMA and to my ears the difference is huge with HE-AAC (either v1 or v2) being the only formats that are listenable at 64kbs, even on a mobile device (I use a Windows Mobile based HTC Touch Cruise smartphone with reasonably good ($120) headphones).

I think that right now you have given more thought to this than me because I was unaware of the possibility that PS only kicks in for HE-AAC v2 at 48kbs or below and, if this is true, then maybe v2 at 48kbs might sound as good as v1 at 64kbs and/or using v2 at 64kbs might give no improvement vs v1 at the same bitrate (my listening tests there were inconclusive so I might need to do more comparisons there).

For me there are other complications. Battery life on my device is very important to me and HE-AAC v2 is a more sophisticated algorithm therefore presumeably needs more CPU cycles to decode every second of music and so will give a shorter playing time per battery charge vs HE-AAC v1. If this is true then it is important enough to me that I will need to think carefully about what level of sound quality I would be willing to trade off against what level of gain in battery life and on this point I'm even going to throw LC-AAC into the mix and do both listening tests and current consumption tests on all 3 formats. I wonder if you (ahavvas) or anyone else ever got into this issue.

Anyway, I'm really interested in anyone's opinions and to see what new answers ahavvas might have found in the last 3 months.

- Julian