Hi, I found an issue while playing with Bayer pixel format conversions.
``` $ echo -ne '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff' > image.raw $ xxd image.raw 00000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000010: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000020: ffff ffff ffff ffff ffff ffff ffff ffff ................ 00000030: ffff ffff ffff ffff ffff ffff ffff ffff ................ ``` And then: ``` $ ffmpeg -y -f rawvideo -pixel_format bayer_bggr8 -s 8x8 -i image.raw -f rawvideo -pix_fmt rgb24 -video_size 8x8 image.raw.rgb ... Assertion srcSliceH > 1 failed at libswscale/swscale_unscaled.c:1310 Aborted (core dumped)ated 2 times ``` The issue relates to the ffmpeg parallelization. ``` $ ffmpeg -y -filter_threads 1 -f rawvideo -pixel_format bayer_bggr8 -s 8x8 -i image.raw -f rawvideo -pix_fmt rgb24 -video_size 8x8 image.raw.rgb ... frame= 1 fps=0.0 q=-0.0 Lsize= 0kB time=00:00:00.00 bitrate=N/A speed= 0x eed=N/A video:0kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.000000% $ xxd image.raw.rgb 00000000: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000010: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000020: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000030: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000040: 0000 0000 0000 0000 0000 0000 0000 0000 ................ 00000050: 7f00 3f7f 0000 7f00 3f7f 0000 0000 0000 ..?.....?....... 00000060: ffff ffff ffff 7fbf ff7f ffff 7fbf ff7f ................ 00000070: ffff ffff ffff ffff ffff ffff ffff ffff ................ 00000080: ffff ffff ffff ffff ffff ffff ffff ffff ................ 00000090: ffff ffff ffff ffff ffff ffff ffff ffff ................ 000000a0: ffff ffff ffff ffff ffff ffff ffff ffff ................ 000000b0: ffff ffff ffff ffff ffff ffff ffff ffff ................ ``` FYI: ``` $ grep processor /proc/cpuinfo |wc -l 64 ``` Problem seems to be that `ff_sws_slice_worker()` [libswscale/swscale.c:1222] tries to slice the input to parallelize the scaling task, in my case in 16 different jobs (gdb'ing the process shows `nb_threads == nb_jobs == 16`). The 8x8 input is therefore divided in eight 8x1 slices (1-pixel height), which eventually breaks in `bayer_to_rgb24_wrapper()` as it asserts `srcSliceH > 1`. The problem is the same in the 3 Bayer conversion functions (`bayer_to_rgb24_wrapper()`, `bayer_to_rgb48_wrapper()`, and `bayer_to_yv12_wrapper()`. Wondering about the right solution: We could just enforce `nb_threads = nb_jobs = 1` for all Bayer inputs. That may be the simplest solution. Or we could make sure that `nb_threads` (and `nb_jobs`) are capped at `input_height / 2` (to ensure at least 2 pixels per thread). Any suggestions? Thanks, -Chema _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".