Vijaydeep Kiran Nadkarni wrote:
All,
I have been trying to resolve an issue that I am facing with McASP
transfer and receive drivers on TI’s DaVinci *TMS320DM6437 DVEVM*.
My workspace does:
· a real-time video decode in one thread and
· a simple audio loopback (only receive and transfer using McASP
driver as illustrated by TI’s DVSDK for DM6437) in another thread.
The audio that I hear at the output is recognizable but noisy (a
crackling noise and what seems to be a distortion of the input). The
noise becomes louder as the volume of the input (audio source)
increases. (The audio source of is clear of any such noise).
Other aspects/clues:
· Audio loopback thread is at a higher priority.
· If the McASP transfer is used to play out audio that is
decoded/stored in memory, not captured (audio data is captured but
discarded), then the audio noise goes away.
· If McBSP is used instead of McASP, the audio noise is still heard.
---
· If the video decode is turned off the audio noise goes away.
· The video decoder uses only QDMA channels, not any EDMA
channels (that might cause a resource clash with McASP driver)
· Video decoder is interfaced via Codec Engine.
· Video decoder uses DMAN and DSKT2 to acquire all resources and
no hard-coding is done in the decoder with respect to acquiring resources.
· Code generation and other tools versions:
o Platform Support Package (PSP) version: 1.00.00.01
o Codec Engine version: 1.20
o Code Composer Studio version: 3.3.38.2
o DSP/BIOS version: 5.31.02
o Code Generation tools: v6.0.10
I do not suspect:
· that the video decoder consumes the entire DSP CPU load or
· that the DDR bandwidth is the constraining factor here.
I was wondering if anyone on this mailing list has encountered a similar
issue, i.e. a noise in audio capture or audio playout when a DSP
software module runs in the background. Please, do help out in case you
have a clue as to what may be causing this audio noise.
Thanks.
Regards,
Vijay
Errata on the DM6441 has
"On DM6441 Silicon Revision 1.3 and earlier, Audio Serial Port (ASP) transfers
may need to originate and
complete from on-chip buffers, either in ARM Internal RAM (TCM) or DSP RAM.
This is due to the fact
that there is no tolerance for audio data dropouts that may occur due to the
delays in DDR2 accesses
from other masters and from unavoidable DDR2 refresh cycles;"
So you may have a similar problem. Trying playing the same data on left and
right channel. If the crackle goes
away, this is probably your problem.
Troy
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