On Thursday 01 November 2001 12:07, Paul Davis wrote: > >I've been experimenting with recording at >16 bit depths (Midiman > > Audiophile and current ALSA CVS). > > been doing it for a couple of years now :)
I wasn't claiming this was anything new, just that I've not done much before, since on my old PC trying anything beyond 16-bit 44.1kHz with snd resulted in too many xruns and it had also appeared that arecord gave more noise (as a fraction of fsd) at 32-bit than at 16 but that was assessed by looking at recordings of silence in snd. > >Since 24-bit files are a right-royal-pain and the ALSA hw device for > > ice1712 uses a format of S32_LE, I've been recording to 32-bit .wav > > files, using both arecord and snd (built with native alsa 0.9x support). > > > >Both produce valid wav files, however there is one awkward difference: > >there's a factor of 256 difference between the scaling, so files recorded > > in snd are inaudible if played back by aplay and files recorded by > > arecord are very clipped when viewed in snd. Both have only 24 > > significant bits (I'd be worried if it were otherwise). > > > >Is there any general consensus as to which is the *right* thing to do? I > > can certainly see that there are valid arguments for both ways of mapping > > 24 bits into 32. (Actually I'm rather surprised that the choice is the > > way round that it is since snd uses floats internally (?) so how does it > > know that the card is really generating 24-bits?). > > the hw params include information on both the sample bit width and > `m<ost>s<ignificant>bits', which tell you how (for example) the 24 bit > data is packed into 32 bits. It is however not clear to me that this is encoded in the header of a normal WAV file (unless bits_per_sample should be 24 for snd's convention). BTW: arecord gets bytes_per_second wrong, it looks as if it gets squashed into a short somewhere, if no-one finds it first I'll have a look through the code when I get home tonight. James -- +------------------------+-------------------------------+---------+ | James Tappin | School of Physics & Astronomy | O__ | | [EMAIL PROTECTED] | University of Birmingham | -- \/` | | Ph: 0121-414-6462. Fax: 0121-414-3722 | | +--------------------------------------------------------+---------+ _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
