> -----Original Message----- > From: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxx> > Sent: Mittwoch, 4. November 2020 18:01 Hi again! > Many thanks for your report. Indeed you managed to create a video that is quite > problematic for CODA. Thanks for looking at it! > I must admit I can't fully wrap my head around your prefetch fix, and how the new > condition would fix this issue. Could you explain it in more detail? I don't have access to the CODA960 documentation, so all my findings are based on tests or code documentation. My starting point was the inline documentation [1]: "If we managed to fill in at least a full reorder window of buffers and the bitstream prefetcher has at least 2 256 bytes periods beyond the first buffer to fetch (...)". The current code checks if there are 512 bytes after the current meta. When I comment out the following break, my test videos are working. So for me, starvation is caused by this statement, because it hinders follow-up metas for performance reasons (the decoder might also start hiccuping with too much data enqueued, but not sure). I did some tests, and basically I found out that the sum doesn't matter, so something like - Meta 2: 1024 - Meta 3: 100 - Meta 4: 100 starves, even if it passes the current check. Next, I thought about "2x 256" is actually not the same as "1x 512". With 2x 256, I could actually got a couple more test videos running, something like: - Meta 2: 650 - Meta 3: 50 - Meta 4: 650 The crafting of such video is quite easy by varying the Group-of-Picture and the resolution. However, then I tried some smaller videos (with meta 2 & 4: 256 < meta < 512) which lead to starvation again. I haven't done additional tests, instead I shared my findings and asked for further documentation hints about the actual starvation criteria. So my solution is just a Proof-of-Concept, found by testing and is not backed by documentation - therefore I am also not sure if it is sufficient or has any side effects. Best regards Benjamin [1] https://elixir.bootlin.com/linux/v5.10-rc2/source/drivers/media/platform/coda/coda-bit.c#L352
