Transcoding combinations UPnP and Internet Radio

[Pastim]

I have struggling to understand the different transcoding combinations available. Apologies for the length of the following, but I would be grateful if someone could confirm, or correct, my understanding.

So this is an attempt to understand the subtleties of transcoding with UPnP and Internet Radio. I will only mention aac and 'unspecified' stream types where the underlying type is in fact aac, for the sake of simplicity. I believe other stream types will all follow the same logic as that for aac.

1. Internet Radio Only

If the only service used is Internet Radio, no transcoding should be specified at all. However, I believe a converter like ffmpeg or avconv may still be needed for HLS streams.

2. UPnP Streams Only

If the only radio service used is Internet Radio streaming via UPnP, then I believe the options are as follows:

a) aac is specified in the stream url or in the m3u file

aac:L16/wav24/-

- aac can be transcoded to any one of the supported output stream types (eg. L16 or wav24), and also made available unchanged (-). A '^' has no effect since the Control Point or Renderer makes the choice, not minimstreamer.

*:L16/wav24/-

- has no effect, since the codec is known

b) aac is not specified, but minimstreamer finds out that it is aac on inspection:

aac:L16/wav24/-

- the Control Point or renderer will choose amongst the defined codecs

aac:L16/wav24^/-

- minimstreamer will always transcode to wav24 (I can't see why this is a useful combination, why not just use aac:wav24? )

*:L16/wav24/-

- the Control Point or renderer will choose amongst the defined codecs

*:L16/wav24^/-

- as above - the '^' has no effect since '*' is specified

3. Both Internet Radio and UPnP devices available

a) aac is specified in the stream url or in the m3u file

aac:L16/wav24/-

- for UPnP, aac can be transcoded to any one of the supported output stream types (eg. L16 or wav24), and also made available unchanged (-).
- what happens for Internet Radio? Does it fail?

aac:L16/wav24/-^

- for UPnP, aac can be transcoded to any one of the supported output stream types (eg. L16 or wav24), and also made available unchanged (-).
- for Internet Radio no transcoding will take place.

*:L16/wav24/-

- has no effect, since the codec is known

*:L16/wav24/-^

- has no effect, since the codec is known

b) aac is not specified, but minimstreamer finds out that it is aac on inspection:

aac:L16/wav24/-

- for UPnP, minimstreamer will default to L16 – I'm not sure if the other values have any effect at all?
- what happens for Internet Radio? Does it fail?

aac:L16/wav24/-^

- for UpnP, minimstreamer will default to no transcoding – I'm not sure if the other values have any effect at all?
- for Internet Radio no transcoding will take place

*:L16/wav24/-

- for UPnP, aac can be transcoded to any one of the supported output stream types (eg. L16 or wav24), and also made available unchanged (-).
- what happens for Internet Radio? Does it fail?

*:L16/wav24/-^

- for UPnP, aac can be transcoded to any one of the supported output stream types (eg. L16 or wav24), and also made available unchanged (-).
- for Internet Radio no transcoding will take place.