Life has been a bit busy lately, so I have only just got around to testing RioPlay since Dave included the high quality down sampling code.

I tried it out today, took me a while to get it working as I forgot that the addresses for the stream servers need to be IP addresses rather than names...

It is almost working perfectly now. Most of the nasty effects of down sampling are gone.

However there is still a problem, on the right channel only there is a crackingly sound. There is no problem on the left channel, it sounds perfect.

The MP2 stream in question is 128kb/s sampled at 48khz (the output from a Psion Wavefinder DAB radio). Here is a sample:

http://www.norman.cx/download/rioplay/radio_4_test.mp2

I have checked the following to narrow down the problem:
- the MP2 plays back correctly on every MP3 player on my PC
- the crackingly still exists if I save a chunk of the stream, name it .MP3 and import it into the Rio Audio Receiver server and play it from there
- the crackling is not being caused by my amp/speakers
- the crackling is present on all the streams coming from my Wavefinder
- the crackling is not present on other streams listed in the streams.cfg file (though I suspect they are all MP3 streams)

Do other people see this with this sample ?

Which version of RioPlay are you using? I'm on 0.29a2 and have also noticed an intermittant low-level crackle on MP2 WF streams, although to be honest I hadn't pinned it down to one channel only. I also hadn't realised that the re-sample code had changed - thought I'd just grown accustomed to the sound! Will do some tests to see if it's only on the left channel.....

Also... do you get the problem whereby if you add other stations (Shoutcast streams) to an active stream and then inadvertantly scroll beyond the end of the stack your Receiver will lock solid, needing a cold re-boot?

I'm on 0.29alpha2 as well, the crackling is on the right channel.

I only ever attempt to play from my WF streams or the ones that come in streams.cfg so I don't know about adding stuff to an active stream.

Also... do you get the problem whereby if you add other stations (Shoutcast streams) to an active stream and then inadvertantly scroll beyond the end of the stack your Receiver will lock solid, needing a cold re-boot?

Yeah, this is a known bug. After taking some time off from Rioplay I'm getting ready to start working on it again, and this is an annoying bug that I intend to fix soon.

As for the resampling code, I haven't changed that yet.

Dave - Thanks for the update. If your're fixing the "scroll beyond the end of the playlist" problem then by far the best behaviour (for me at any rate) would be for a scroll forwards beyond the last entry to return to the first entry, and a scroll backwards from the first entry to return to the last - not sure how easy this is to achieve?

Thanks, as ever, for a really great piece of work...

Phil

the crackling is on the right channel

I've done some more testing and listening since. It turns out that there is some crackling on the left channel, it is just very quiet. The crackling sounds very much like clipping. It is definitely not caused by my amp or speakers as it occurs on the headphone output of the Rio as well.

The cracking gets worse as the level of the signal on the channel increases. There are no crackles when the signal on the channel is silent.

I've tested decoding the problem MP2s with other apps that use the same version of the MAD library and no crackling. Which points the finger at the resampling code.

I've also taken a look at the resampling code in the RioPlay source and I'm puzzled. I can't see anywhere that the left and right channels are treated any differently, so I can't see how the crackling can be being generated in the resampling code.

I guess I need to go and play with an MP2 encoder and encode some 44.1khz and 48khz files to see whether the crackling only happens when resampling is happening.