Video dec stats confusing.

[alatteri]

In the below log sequence, I am showing no packet loss, and yet every minute it is printing '1360 missing'.

What does that indicate?

[2021-08-05 14:30:43] SSRC 3f1e3bd5: 12160/12160 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:30:43] Video dec stats (cumulative): 37799 total / 36439 disp / 0 drop / 167 corr / 1360 missing.
[2021-08-05 14:30:43] [SDL] 120 frames in 5.00516 seconds = 23.9752 FPS
[2021-08-05 14:30:48] SSRC 3f1e3bd5: 12032/12032 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:30:48] [SDL] 120 frames in 5.00034 seconds = 23.9984 FPS
[2021-08-05 14:30:53] SSRC 3f1e3bd5: 12416/12416 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:30:53] [SDL] 120 frames in 5.0083 seconds = 23.9602 FPS
[2021-08-05 14:30:58] SSRC 3f1e3bd5: 12288/12288 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:30:58] [SDL] 120 frames in 5.01311 seconds = 23.9372 FPS
[2021-08-05 14:31:03] SSRC 3f1e3bd5: 11904/11904 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:03] [SDL] 121 frames in 5.03501 seconds = 24.0317 FPS
[2021-08-05 14:31:08] SSRC 3f1e3bd5: 12160/12160 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:08] Video dec stats (cumulative): 38399 total / 37039 disp / 0 drop / 167 corr / 1360 missing.
[2021-08-05 14:31:08] [SDL] 120 frames in 5.00743 seconds = 23.9644 FPS
[2021-08-05 14:31:13] SSRC 3f1e3bd5: 11776/11776 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:13] [SDL] 120 frames in 5.003 seconds = 23.9856 FPS
[2021-08-05 14:31:18] SSRC 3f1e3bd5: 11264/11264 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:18] [SDL] 120 frames in 5.01228 seconds = 23.9412 FPS
[2021-08-05 14:31:23] SSRC 3f1e3bd5: 11392/11392 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:24] [SDL] 121 frames in 5.03843 seconds = 24.0154 FPS
[2021-08-05 14:31:28] SSRC 3f1e3bd5: 10880/10880 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:29] [SDL] 120 frames in 5.00771 seconds = 23.9631 FPS
[2021-08-05 14:31:33] SSRC 3f1e3bd5: 8960/8960 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:33] Video dec stats (cumulative): 38999 total / 37639 disp / 0 drop / 167 corr / 1360 missing.
[2021-08-05 14:31:34] [SDL] 120 frames in 5.00247 seconds = 23.9882 FPS
[2021-08-05 14:31:38] SSRC 3f1e3bd5: 8448/8448 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:39] [SDL] 120 frames in 5.0021 seconds = 23.9899 FPS
[2021-08-05 14:31:43] SSRC 3f1e3bd5: 9600/9600 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:44] [SDL] 120 frames in 5.00424 seconds = 23.9797 FPS
[2021-08-05 14:31:48] SSRC 3f1e3bd5: 9216/9216 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:49] [SDL] 120 frames in 5.01203 seconds = 23.9424 FPS
[2021-08-05 14:31:53] SSRC 3f1e3bd5: 8832/8832 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:54] [SDL] 120 frames in 5.00599 seconds = 23.9713 FPS
[2021-08-05 14:31:58] SSRC 3f1e3bd5: 8960/8960 packets received (100%), 0 lost, max loss 0.
[2021-08-05 14:31:58] Video dec stats (cumulative): 39599 total / 38239 disp / 0 drop / 167 corr / 1360 missing.
[2021-08-05 14:31:59] [SDL] 121 frames in 5.04658 seconds = 23.9766 FPS

[MartinPulec]

Hi @alatteri, those decoder statistics are cumulative, so it looks legit to me - no packet loss -> no increase in corrupted/missing frames. Of course I cannot say that those values are correct without the history. But those values would indicate that there were some few-seconds outages (more missing frames than corrupted - the corruption would then occur typically at the beginning and end of the outage).

[alatteri]

Thanks Martin.... That makes sense, I see (cumulative) now. I thought it was "current".

[MartinPulec]

Sure, we thought that the cumulative count may be more useful (eg. if you leave UG running all night) while the current values are for the packet loss (so both spans are complementary).