Metrics from the latency subsystem

[Vineet Krishnan]

Hello,

I'm looking into the Tracing subsystem
<https://gstreamer.freedesktop.org/documentation/additional/design/tracing.html?gi-language=c#try-it>
to
measure processing latency in our gstreamer pipeline. On running the
generated file through gst-stats, I get the following output -


Latency Statistics:
    0x7fd35e827ce0.audiotestsrc0.src|0x7fd35c813290.rtmpsink0.sink:
mean=0:00:00.059332305 min=0:00:00.003686000 max=0:00:00.782444000
    0x7fd35d0082e0.videotestsrc0.src|0x7fd35c813290.rtmpsink0.sink:
mean=0:00:00.043311752 min=0:00:00.003628000 max=0:00:00.797304000

Element Latency Statistics:
    0x7fd35d030190.capsfilter0.src: mean=0:00:00.000519092
min=0:00:00.000263000 max=0:00:00.001867000
    0x7fd35e830240.audiomixer0.src: mean=0:00:00.023331131
min=0:00:00.001518000 max=0:00:00.774963000
    0x7fd35e82f4d0.audioconvert0.src: mean=0:00:00.000393081
min=0:00:00.000143000 max=0:00:00.011368000
    0x7fd35d034150.x264enc0.src: mean=0:00:00.003406024
min=0:00:00.002231000 max=0:00:00.006731000
    0x7fd35e82fc70.faac0.src: mean=0:00:00.000625431 min=0:00:00.000355000
max=0:00:00.003427000
    0x7fd35e830540.mux.src: mean=0:00:00.036701334 min=0:00:00.000177000
max=0:00:00.792271000


I couldn't find a definitive explanation of these numbers by searching
online, so I wanted to verify if my understanding is correct.

For the line

0x7fd35e827ce0.audiotestsrc0.src|0x7fd35c813290.rtmpsink0.sink:
mean=0:00:00.059332305 min=0:00:00.003686000 max=0:00:00.782444000

Does it mean that there was a mean latency of 0.059s and a max latency of
0.78s to propagate a buffer from the audiotestsrc to the rtmpsink? If yes,
would this represent the end-to-end processing latency of this source->sink
path?

Similarly, for the element latency statistics -

0x7fd35d034150.x264enc0.src: mean=0:00:00.003406024 min=0:00:00.002231000
max=0:00:00.006731000

Does it mean that the x264enc is adding 0.006s processing latency?


Thanks!
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