Sansa e200 v1: HE-AAC/AAC+ playback

[vinnie97]

I had been out of the Rockbox loop for a while but upon checking in the last few days and updating to the latest version, I see that they've managed to incorporate an open source decoder for this excellent-sounding format.  The one caveat I've experienced with his hardware/codec combination is interrupted playback, making it unlistenable.  I tried disabling features in the options but couldn't get smooth playback.  Is this just a CPU limitation or will further decoder tuning garner any possibility of smooth playback in the near future?  I fear it may be due to the former and I may need to get a Rockbox supported player with a faster CPU if I want the feature.

EDIT:  And NOW I found this thread:  http://forums.rockbox.org/index.php?topic=21991.0

It confirms my suspicion that the v1 clock is to blame.  Blast!

[saratoga]

The one caveat I've experienced with his hardware/codec combination is interrupted playback, making it unlistenable.  I tried disabling features in the options but couldn't get smooth playback.  Is this just a CPU limitation or will further decoder tuning garner any possibility of smooth playback in the near future? 

AAC-HE is one of the slowest formats in widespread use, but it should eventually be possible to decode it on the e200v1.  We've been slowly improving the AAC decoder, but not the HE part yet. 

[vinnie97]

^That's great news, thanks!  So there is room for further fine-tuning in the HE dept (I thought it was added relatively recently).  Do you have a ballpark estimated timeline on when the code will be efficient enough to run smoothly on this device?  It makes sense that it's the most resource-intensive, as it also produces the greatest transparency around 64kbps (or at least that was the case a few years ago and Vorbis and WMAPro were the only actively developed formats that came close).

[Llorean]

Timelines are impossible. It's entirely possible nobody will ever bother working on it. It's entirely possible someone will show up with a patch 5 minutes from now that they'd been working on recently.

It's a volunteer effort. Please, just don't ask for estimates on when things might be done.

[saratoga]

^That's great news, thanks!  So there is room for further fine-tuning in the HE dept (I thought it was added relatively recently).  Do you have a ballpark estimated timeline on when the code will be efficient enough to run smoothly on this device? 

Probably not too long after someone takes an interest in working on it.

[vinnie97]

A year later, I see the progress for this codec on this hardware is still not realtime and that the effort to make it happen is probably not worth it, especially since the equally as impressive WMAPro runs efficiently now.

[saratoga]

I don't think WMA Pro really has much to do with AAC-He since they do fairly different things, but improving all codecs is worthwhile anyway. 

[vinnie97]

Well, their performance at bitrates below 100kbps is where they shine the brightest.  In all double-blind listening tests I've seen conducted, these 2 codecs along with Vorbis have consistently performed the most impressively...and I realize the technical manner in which they achieve this transparency determines key factors like decoding power requirements.

I meant it's likely not worth it in the sense of someone waiting to use HE-AAC on this hardware, unless they can and are willing to optimize it themselves.

[saratoga]

Well, their performance at bitrates below 100kbps is where they shine the brightest.  In all double-blind listening tests I've seen conducted, these 2 codecs along with Vorbis have consistently performed the most impressively...and I realize the technical manner in which they achieve this transparency determines key factors like decoding power requirements.

WMA Pro is a normal high bitrate codec like Vorbis, AAC, WMA, or MP3.  AAC-He is a specialized codec that only works at very low bitrates.  I meant that its very weird to compare them since they're usually used for different things.

[vinnie97]

Well, anything below 64kbps and I am generally bothered by the artifacts even for mobile listening.  However, independent testing has shown WMA Pro to be highly competitive in the 48-64kbps range at the very least:


multiformat 48 kbps ABX test


multiformat 64 kbps ABX test

This trio of formats seems to be the most well suited to this range, and it's hard to go wrong with any of the above.  Given the additional tuning HE-AAC and Vorbis (at least) have received since the tests (2006-7), this may not be as representative of the reality today.  

This is why I compare them, as they have similar psychoacoustic performance at a bitrate range that interests me in the personal/portable audio arena.