Sponsoring a feature? (Support for HiRes-Audio, 24/96 or 24/192)

[ElEsido]

Thanks Llorean!

[saratoga]

saratoga, you said that rockbox might be able to output 20bit through SPDIF. Someone tested this here with an iriver ( http://www.head-fi.org/forums/f15/who-has-iriver-h1xx-dac-amp-shows-bitrate-optical-spdif-input-465137/#post6294363]) and only got 16bit.

Ok then my assumption would be that the hardware is not 20 bit capable.

I have a more geeky approach to this: High-rez files are available, disk space is no longer an issue for hard disk DAPs, there are external dacs and many DAPs have dac chips that decode 24/06, so why not do it.

96khz is very mildly useful for recording, mixing and editing, but for playback via optical is just a marketing gimmick, and one that would significantly reduce battery life at that.

Basically 'because its completely useless and has serious costs associated with it'. 

That said supporting 48k makes a lot of sense and we don't do that, so eventually making the PCM system more independent of sampling rate would be a good idea.

[Multiplex]

Ok then my assumption would be that the hardware is not 20 bit capable.

The datasheet for the specific hardware used in the H100 is available from the Wiki. I've had a scan and as I read it the Codec hardware should be capable of outputting 24 bit at 96k, now there are plenty of other bits (like the output hardware and the ability of the CPU to shovel data at the codec fast enough) that may meant that the overall system may not be able to do it.

Not that I'm in the slightest bit interested in high res audio... Just intrigued by the discussion.

[Llorean]

I seem to remember also being told that the upper limit factoring in everything was 20/44 or 20/48 (I can't remember which) for the h100 series.

[Blue Dude]

The way things are now, everything gets converted to the native format of 44.1k/16 when it comes out of the DSP process.  The internal format is frequency and bit depth flexible (set by the codec), so a lot of the code just doesn't care about it.  It is *possible* to output other formats, but right now everything past the DSP (playback, PCM buffer, hardware drivers) expects the native format in order to function properly.  With all that said, given hardware/driver that accepts other formats (and adequate RAM for buffering), I see nothing at first glance that would prevent a fairly trivial rewrite that would allow basic playback of deeper formats.  Some things (crossfade comes to mind) would require a lot more RAM, but could be disabled or limited in function to allow the PCM buffer to expand adequately.  You might also need to give up some DSP effects that may choke on high data rates.  Some codecs might be capable of decoding high res audio correctly without significant modification but then cause underruns due to high data rates.  It's hard to say for sure until it's tried.