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Tracer subsystem, how to interpret these measures?

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solo_juan
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Tracer subsystem, how to interpret these measures?

solo_juan
Hi,

I'm learning Gstreamer. I'm trying to use the *Tracer* subsystem but I don't
know how to interpret the measurements.

The data:

- Rasberry Pi 3
- Raspbian Buster
- Raspberry Camera Module V2
- gstreamer, version 1.17.1
- Capture data: Motion-JPEG, 426x240 and 429000 bps of bitrate

*Pipeline 1 (15 fps):*

/opt/vc/bin/raspivid -t 60000 -cd MJPEG -w 426 -h 240 -fps 15 -b 429000 -vf
-hf \
-o - | GST_DEBUG="GST_TRACER:7" GST_DEBUG_FILE=240.log
GST_TRACERS="latency(flags=pipeline+element+reported)" \
gst-launch-1.0 -v  fdsrc do-timestamp=true ! \
"image/jpeg,width=426,height=240,framerate=15/1,payload=(int)26" ! \
jpegparse ! rtpjpegpay ! \
udpsink port=13000 host=192.168.1.111 && gst-stats-1.0 240.log

*Measure (pipeline 1):*

Latency Statistics:
0x20340f0.fdsrc0.src|0x20ff150.udpsink0.sink: mean=0:00:00.001291400
min=0:00:00.000751041 max=0:00:00.007009887

Element Latency Statistics:
0x21040f0.capsfilter0.src: mean=0:00:00.000236961 min=0:00:00.000096875
max=0:00:00.000554530
0x20ec2d0.jpegparse0.src: mean=0:00:00.000558282 min=0:00:00.000346250
max=0:00:00.006139732
0x20f80b8.rtpjpegpay0.src: mean=0:00:00.000458047 min=0:00:00.000248542
max=0:00:00.004859044

Element Reported Latency:
0x20340f0.fdsrc0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.644349393
0x21040f0.capsfilter0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.644468508
0x20ec2d0.jpegparse0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.644528403
0x20f80b8.rtpjpegpay0: min=0:00:00.000000000 max=99:99:99.999999999
ts=0:00:00.644595383


*Pipeline 2(rpicamsrc, 30 fps):*

GST_DEBUG="GST_TRACER:7" GST_DEBUG_FILE=240p.log
GST_TRACERS="latency(flags=pipeline+element+reported)" \
 gst-launch-1.0 rpicamsrc preview=0 rotation=180 bitrate=4429000 ! \
 image/jpeg,width=1270, height=720,framerate=30 ! \
 jpegparse ! rtpjpegpay ! port=13000 host=192.168.1.111 && gst-stats-1.0
240p.log

*Measure (pipeline 2):*

Latency Statistics:
0x485738.rpicamsrc0.src|0x550e98.udpsink0.sink: mean=0:00:00.002029413
min=0:00:00.000996300 max=0:00:00.007922902

Element Latency Statistics:
0x556118.capsfilter0.src: mean=0:00:00.000220204 min=0:00:00.000116354
max=0:00:00.000882290
0x53c2e8.jpegparse0.src: mean=0:00:00.000840342 min=0:00:00.000421510
max=0:00:00.006688112
0x54a0c8.rtpjpegpay0.src: mean=0:00:00.000968794 min=0:00:00.000458436
max=0:00:00.006141604

Element Reported Latency:
0x485738.rpicamsrc0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473207970
0x556118.capsfilter0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473302137
0x53c2e8.jpegparse0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473359064
0x54a0c8.rtpjpegpay0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473419220

I understand that in the first pipeline, it takes *644.3* ms o receive the
data stream from the camera and in the second pipeline it takes *473.2* ms.

Is this interpretation of the data correct? If so, why does it take so long
to acquire the flow?

Cheers.



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Nicolas Dufresne-5
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Re: Tracer subsystem, how to interpret these measures?

Nicolas Dufresne-5


Le dim. 2 févr. 2020 10 h 30, solo_juan <[hidden email]> a écrit :
Hi,

I'm learning Gstreamer. I'm trying to use the *Tracer* subsystem but I don't
know how to interpret the measurements.

The data:

- Rasberry Pi 3
- Raspbian Buster
- Raspberry Camera Module V2
- gstreamer, version 1.17.1
- Capture data: Motion-JPEG, 426x240 and 429000 bps of bitrate

*Pipeline 1 (15 fps):*

/opt/vc/bin/raspivid -t 60000 -cd MJPEG -w 426 -h 240 -fps 15 -b 429000 -vf
-hf \
-o - | GST_DEBUG="GST_TRACER:7" GST_DEBUG_FILE=240.log
GST_TRACERS="latency(flags=pipeline+element+reported)" \
gst-launch-1.0 -v  fdsrc do-timestamp=true ! \
"image/jpeg,width=426,height=240,framerate=15/1,payload=(int)26" ! \
jpegparse ! rtpjpegpay ! \
udpsink port=13000 host=192.168.1.111 && gst-stats-1.0 240.log

*Measure (pipeline 1):*

Latency Statistics:
0x20340f0.fdsrc0.src|0x20ff150.udpsink0.sink: mean=0:00:00.001291400
min=0:00:00.000751041 max=0:00:00.007009887

Element Latency Statistics:
0x21040f0.capsfilter0.src: mean=0:00:00.000236961 min=0:00:00.000096875
max=0:00:00.000554530
0x20ec2d0.jpegparse0.src: mean=0:00:00.000558282 min=0:00:00.000346250
max=0:00:00.006139732
0x20f80b8.rtpjpegpay0.src: mean=0:00:00.000458047 min=0:00:00.000248542
max=0:00:00.004859044

Element Reported Latency:
0x20340f0.fdsrc0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.644349393
0x21040f0.capsfilter0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.644468508
0x20ec2d0.jpegparse0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.644528403
0x20f80b8.rtpjpegpay0: min=0:00:00.000000000 max=99:99:99.999999999
ts=0:00:00.644595383


*Pipeline 2(rpicamsrc, 30 fps):*

GST_DEBUG="GST_TRACER:7" GST_DEBUG_FILE=240p.log
GST_TRACERS="latency(flags=pipeline+element+reported)" \
 gst-launch-1.0 rpicamsrc preview=0 rotation=180 bitrate=4429000 ! \
 image/jpeg,width=1270, height=720,framerate=30 ! \
 jpegparse ! rtpjpegpay ! port=13000 host=192.168.1.111 && gst-stats-1.0
240p.log

*Measure (pipeline 2):*

Latency Statistics:
0x485738.rpicamsrc0.src|0x550e98.udpsink0.sink: mean=0:00:00.002029413
min=0:00:00.000996300 max=0:00:00.007922902

Element Latency Statistics:
0x556118.capsfilter0.src: mean=0:00:00.000220204 min=0:00:00.000116354
max=0:00:00.000882290
0x53c2e8.jpegparse0.src: mean=0:00:00.000840342 min=0:00:00.000421510
max=0:00:00.006688112
0x54a0c8.rtpjpegpay0.src: mean=0:00:00.000968794 min=0:00:00.000458436
max=0:00:00.006141604

Element Reported Latency:
0x485738.rpicamsrc0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473207970
0x556118.capsfilter0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473302137
0x53c2e8.jpegparse0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473359064
0x54a0c8.rtpjpegpay0: min=0:00:00.000000000 max=0:00:00.000000000
ts=0:00:00.473419220

I understand that in the first pipeline, it takes *644.3* ms o receive the
data stream from the camera and in the second pipeline it takes *473.2* ms.

Is this interpretation of the data correct? If so, why does it take so long
to acquire the flow?

This is not what the latency tracer measure. It mesure the latency added by the pipeline while processing the frames. In your case, it says you have about 1ms latency, which is near to nothing. Basically it's the average processing delay. This is considered zero-latency.

The ts= value is the time the trace was recorded. Reported latency can be changed at run-time by elements, so we have to add this information here in order to differentiate the records. What it says is that it took 473 and 644ms for the pipeline to reach a point we're latency could be calculated. This is likely close to when the pipeline started streaming, but this is just correlation, and not the intended information.

Measure the glass to glass latency is not possible from a tracer. You need special streams and equipment to achieve this.



Cheers.



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