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Subject: Re: WAV Codec for Archos

Re: WAV Codec for Archos

From: Christoph Niedeggen <Niedeggen_at_gmx.net>
Date: 2006-01-24

Hi Jörg,

> Patching the PCM codec into Rockbox for Archos is not not a trivial task. If
> done properly, it's an opportunity to renovate the playback+recording code,
> like keeping the bitswap away from the big buffer, a different concept for
> metadata of buffered files, a frame walker for mp3, trick modes, etc. I'd
> liked to have done that, but other priorities got in the way.

That's a pity! But does it really need to renovate the whole playback
and recording code and do the other things you mentioned?

As a start I would be completely happy if someone wrote a plugin for
WAV/PCM recording and a plugin (probably a viewer!?) for WAV/PCM playback!

> For full quality wav pumping, our poor CPU would be pretty busy with
> bitswapping.

Could you explain why the recorded data has to be bitswapped? Do the
most significant byte and the least significant byte have to be swapped
in order to get a proper WAV stream?

It would be perfectly alright as a start to just be able to write the
plain PCM data to disk (with the said plugin) and to do the post
processing (e.g. bit swapping and adding of a WAV header) later on the
PC. This would also prevent the Jukebox CPU from becoming too busy.

> Don't let your expectations fly too high about running codecs
> on it, too. The disk will be busy, too, having 8 MB helps.

Right. Having 8 MB means that the buffer has to be written to disk every
45 seconds when recording 44.1 kHz, stereo. But that should still be OK.

> I'm not worried about audio quality. When using S/PDIF, it's 1:1, as much as
> you can get.

I think that even recordings made via the Line-In might benefit from a
WAV/PCM recording if the analogue input level is high enough so that the
built-in amplifier does not have to be set to a high gain (thus
producing more noise.)

Christoph
Received on Tue Jan 24 23:38:54 2006


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