Sorry for the delayed reply; I didn't see this message somehow! seanadams Wrote: > Nice work!Thanks! I've run into a bit of a wall though, which I'll explain > at the end (I'm not sure if I'm now trying to do something the firmware doesn't like). > Is there a good way of tagging the FLAC files to indicate that they > contain DTS or AC3 instead of PCM? If so, then a future firmware rev > could do a couple things: > > - set various s/pdif control bits to reflect non-PCM data (not that any > receivers care AFAIK). > - Disable the analog outputs > I'm not sure about a "good" way... I wonder if the FLAC format allows for any format-identifying metadata (not tags, but in the format itself). I'll look into that. For now I've just added an SPDIF_ONLY tag to my FLACs, with a value of something like "Dolby Digital". I'm sure there are better ways! I'd also like to prevent these FLACs being played in fb2k, but I think that's less likely to happen magically. > Also if you're willing to share your code under the BSD license we could > consider porting it to the firmware so that raw DTS or AC3 can be > streamed down (although this is probably not as good as FLAC since > there'd be no tagging).I'd be happy to do so. I did look at some other > utilities when I got stuck (although one, which I couldn't compile to actually test, looked like it wouldn't work so I did the opposite of what it said). When writing a utility for oneself, this is not a problem; when offering the code to the world, I guess it can be. I'll check the licences of the code I looked to for help; they're "open" or I wouldn't have been looking at them.
Conversion in the firmware might solve a problem I had with using my utility as a run-time converter (apart from the fact that I couldn't get it to easily be invoked, it being Python and not a exe file): writing an accurate WAV header was dependent on a consistent frame size throughout the source file. With a test AC3 file from a DVD, the frame size was consistent and I could write an estimate to the header which turned out to be correct. With a different test downloaded from 'NRK.no' (http://www.nrk.no/ulyd/0.html?p_saksunivers_id=24360) I found the frame size varied over the file, so the header estimate wasn't right. When I'm relying on writing a valid WAV file so that the SB2 will play it, this can be a problem. It might be less of an issue using the firmware directly (the playing-time estimate may be wrong, but the box can play until end-of-stream). Now, the problem I've run into: DTS files are oh-so-close to working, but not quite. I've converted one in the way I understood to be correct, and it plays back at a third of the right speed. This is probably because it's in a WAV file marked as 48000 Hz, with an average bytes per second of 192000. The real bytes per second value should be three times that, but if I set the WAV header to reflect that (increasing the bps and the block align by a factor of three) the file doesn't play at all. Is there a maximum bitrate that the SB2 can pass through to the receiver? (The AC3 files have each frame padded to 6144 bytes, but there seem to be three times as many frames in a DTS file than in an AC3 file of similar length.) To work around this factor of three problem, I've also tried reducing the size of the file -- by padding to 2048 bytes instead of 6144. This seems like a much better plan (although I haven't found any specs which tell me why I should be doing that!) -- but again it doesn't quite work. I get 5 seconds of working DTS audio (I get teased by the intro to the song!) before silence for the rest of the file. The DTS light on my receiver stays on, but I don't know if it's just being optimistic or if it is still receiving the data. I'll do some more research this week (my day job is creeping into evenings a bit at the moment, so I have less time to work with), but in the mean-time I'd be interested to know of any limitations in the firmware which I might be running into. Cheers, Steve -- smst _______________________________________________ audiophiles mailing list [email protected] http://lists.slimdevices.com/lists/listinfo/audiophiles
