Hi Philipp, On 02/03/17 10:19, Philipp Zabel wrote:
I don't know what the BWB unit is, I guess W is for write and one of the Bs is for burst. All I know is that there repeatedly have been issues with it hanging on certain streams (ENGR00223231, ENGR00293425), with various firmware versions, sometimes blocking something related to the GDI bus or the GDI AXI adapter. There are some error cases that we don't know how to recover from without a reboot. Apparently this unit can be disabled by setting bit 12 in the FRAME_MEM_CTRL mailbox register to zero, so do that to avoid crashes.
Both those FSL ENGR patches to Android and VPU lib are specific to decode, with the first being specific to VC1 decode only.
Side effects are reduced burst lengths when writing out decoded frames to memory, so there is an "enable_bwb" module parameter to turn it back on.
These side effects are dramatically reducing the VPU throughput during H.264 encode as well. Prior to this patch I was just about managing to capture and stream 1080p25 H.264. After this change it fell to about 19fps. Reverting this patch (or presumably using the module param) restores the frame rate.
Can we at least make this decode specific? The VPU library patches do it in vpu_DecOpen. I'd guess disabling the BWB any time prior to stream start would be OK.
It might also be worth adding some sort of /* HACK */ marker, since disabling the BWB feels very like a hack to me.
Regards, Ian
