Upsampling to 176.4/192 and transcoding

[simoncn]

(28-12-2012 01:50)Alekz Wrote:  How difficult possible is it to implement 2x/4x upsampling feature?

For example:

from 44.1 to 88.2 and 176.4
from 88.2 to 176.4
from 48 to 96 and 192
from 96 to 192

The improvement (along with 16->24bit conversion) is subtle, but still noticeable.

The simplest solution would be to spawn an external program - sox, which is available for every OS. Or even add a new config file for transcoding/conversions with SOX/mac/flac command lines (less programming). So, whether this feature is needed or not, MinimServer will stay as compact as possible, yet will support more formats (e.g. APE, WV, etc.)

Minimserver currently supports transcoding from FLAC to WAV, with optional 16->24 bit padding of audio samples.

The next step is to extend this to other transcoding combinations, such as FLAC to L16 and ALAC to WAV. I've had user requests for both of these.

I've been doing some prototyping of using an external converter to add more transcoding combinations (including the above), and I've got an early prototype working with ffmpeg or libav as the converter. It shouldn't be very difficult to add sox as another converter option.

I haven't done any work on upsampling yet. I'm using an upsampling player (Linn DS), so I suspect this wouldn't provide any benefit in my system. It might be useful for other users, though.

It isn't possible to use an external converter to add support to MinimServer for filetypes that MinimServer doesn't understand. This is because MinimServer needs to read the audio information and tag data for all files in the user's library.

For playback with transcoding (or upsampling), the need to support file seeking means that MinimServer needs to understand both the original format and the transcoded/upsampled format.

I'm still experimenting with some aspects of this, so it's hard to say at this stage when it will be released. I hope I'll have something ready to release in the fairly near future.