#milkymist IRC log for Monday, 2013-09-23

zumbihello! maybe this is not the right channel, but I'll ask, which is good and inexpensive option to be able to play/decode audio streams?20:24
zumbiI was thinking on cortex-m based thingy20:25
zumbimaybe something fpga based is better20:26
ysionneauI don't think you need FPGA to decode audio20:29
ysionneausmall cpu can do it I think20:29
ysionneauit depends on the encoding20:29
ysionneauwhich format do you want to decode ?20:29
ysionneauI don't remember if we tried decoding mp3 on LM32 on FPGA20:30
ysionneaubut I bet any arm core can do it with their bunch of hundreds of MHz20:30
acathlathere are microcontrolers specialized for that, like the portalplayer µP20:32
davidc__I've done MP3 decoding on a 70mhz ARM7TDMI20:32
davidc__'twas a portalplayer, actually (they don't have any fancy HW support)20:32
ysionneauso even a 75 MHz PIC32 might be able do to it20:35
ysionneauto do it*20:35
davidc__hardware multiplier and fast barrel shifter are key IIRC. The Helix decode library is quite good (all fixed point) but it has a bit of a funky license20:37
zumbithanks guys.. I wanted to play streams, so better if I add some audio decoding chip20:43
zumbiand leave CPU for network activity20:44
zumbihowever I am looking to that helix libs20:44
zumbisounds interesting20:44
acathlaexternal decoding chip was used in firsts MP3 players, now acceleration is integrated in the µP20:48
acathlaand hardware decoder decodes ONLY what's it's designed for, like only MP320:49
zumbiacathla: I was thinking on VS105320:50
zumbiOgg Vorbis / MP3 / AAC / WMA / FLAC / MIDI Audio Codec Chip20:51
davidc__zumbi: why not just drop down a 200+mhz ARM? They're cheap and have plenty of horsepower.20:52
acathlaou still need a microcontroller, but probably with less code to write20:52
zumbidavidc__: I was thinking on some ARM based device running some kind of linux, but, I was targeting a device per room20:56
zumbiso, low cost and high quality audio is interesting.. but it might be easier to use on of those raspberry pi boards (which does not do hw audio decoding) and most devices quality is crap20:57
zumbiaudio quality*20:57
acathlawhat's the link between audio quality and decoding from a chip or another?20:59
acathlathe quality will be made by our DAC and amplifier21:00
zumbiwell, yes, I meant DAC on ARM dev boards is usually bad21:04
acathlausing an external decoding chip won't solve the problem, unless it has an embedded DAC21:06
zumbicortex-m4 can do 32-bit single cycle MAC ops21:09
Hawk777acathla: the STM32F4Discovery board (used to be insanely cheap, $15 IIRC) has a nice ARM chip and a CS43L22, audio DAC with integrated class D speaker driver on the board, among other things. I have no clue what the audio quality of that chip is (Ive never used it), but it might help you.21:38
Hawk777The CPU runs up to 168 MHz.21:38
Hawk777No hardware decoder, but it might be beefy enough to run a software decoder.21:38
Hawk777(and zumbi)21:39
zumbinah! it does not have ethernet.. I know those boards21:42
Action: zumbi needs to review class D speaker driver21:42
Hawk777Oh, I didnt know Ethernet was a requirement.21:43
Hawk777The MCU does though, so if youre thinking of custom boards its still on the table.21:44
zumbiI am being deviated to something based on raspberry pi and use hdmi audio22:00
--- Tue Sep 24 201300:00

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