[En-Nut-Discussion] stammering audio playback on EIR/VS1053B

[Bonnemayer C (PSYCHOLOGY)]

Dear all,

Being a starter with Nut/OS I tried some NutWiki examples to gain some knowledge about this OS. As a Nut/OS newbee I hope you can forgive me for possible stupid questions.

With a slightly modified version of the NutWiki MMC MP3 player I tried to play .ogg and .flac files (the latter with the VS1053B patch v1.95) on my EIR board.  It appears that when using high quality files (with low compression and/or high bitrates) the output is interrupted during playback. I.e. the file plays for a second or so, waits for half a second, and then continues where it has left, this happens intermittentally.  I tried several audio formats and to me it seems that high bitrate files (mp3  > 192 kbps, ogg >  44.1KHz, 147kbps) have more problems than low bitrate files.
I played around with some settings, but changing VSCODEC0_OUTPUT_BUFSIZ in audio.h doesn't help. Also, changing VSCODEC0_SPI_RATE has no effect.

it looks like that the problem lies in the fact that the VS1053 codec shares the SPI bus with the MMC interface, so there's a lot of data trafic on this bus. Unfortunately I don't have a logic analyzer, so I can't verify this.

Does anybody has any suggestions for further troubleshooting?

Best regards,

Charles Bonnemayer

Hardware: EIR board with VS1053 audio codec
software: Nut/OS 4.10.1, Yagarto with GCC-4.6.2
Win OS: Windows XP SP3