Jerry Johns wrote: > Hey all, > > I'm using the DM355 chip mated with an FPGA that produces an > I2S compliant bit stream - I did not have to modify the davinci audio > drivers since the FPGA produces an exact bitstream as the TLV320AIC33 > chip does (16 bit samples, L and R on a I2S line); On the application > side, I'm using the encode demo to do both video and audio capture to > files. > > > > I'm noticing a few things on the encode demo application - the FPGA can > be setup to produce a test stream (the I2S 16 bit samples increase by 1, > like a counter so that we test for dropped samples on the DM355); When > using the test stream, I find that if I don't do video encoding, the > bitstream received by the DaVinci is 'perfect' - there are no > repeats/drops in the increasing count values. > > > > When I enable video encoding, I start getting random single sample drops > in the received bitstream, i.e the counter values occasionally increase > by 2 > > I'm using the stock encode demo application. > > > > Initial hunch seems to tell me that it could be a EDMA problem, due to > bus overloading. However, it is always 1-2 samples. It doesn't make > sense that it could be a timing problem - a constant, periodic 1-2 > sample drop could not be caused by bus delays since video and audio both > have independent bitrates and are asynchronous, leading to complex > memory access patterns. > > > > I don't think others have noticed this problem on the 355/6446 since > there was no way to conclusively detect single sample drops from the ADC > (it doesn't have a test mode) and you can only notice this when using an > FPGA that can generate custom test patterns. However, this could > manifest on the DVEVM boards as channel swaps > > > > Anyone have any clue? > > > > Thanks a bunch! > > > > Jerry >
The asp channel (McBsp) on the dm6446 has the same issue. It is in TI's errata to use ping/pong IRAM to fix the problem. The first patch of a group is coming today. Troy _______________________________________________ Davinci-linux-open-source mailing list [email protected] http://linux.davincidsp.com/mailman/listinfo/davinci-linux-open-source
