wiki:Yocto/gstreamer/latency

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Version 2 (modified by Chris Lang, 7 years ago) ( diff )
--

Latency

Latency

Latency is the term used to describe how long it takes for video from the source side to get to the sink side. For example, if a video system was described as having a latency of 1 second, that would mean that it takes 1 second for the video to get from the capture (or reading a file) side to the actual display.

This section will attempt to describe some real world latencies that we have seen using gstreamer and our product. Because latency is highly dependent on the different 'knobs' that you can turn, each section will be a very specific test setup. This is important, as you cannot reliably compare latencies when you start to introduce/remove certain feature, video capture ports/types, sink types etc.

The below values differ in capture/display device+driver in the following ways that affect latency

Frames Per Second (FPS)
Interlace vs. Progressive
Capture device Output format (RAW vs JPEG)
Capture device's inherent latency
Display device's inherent latency

Please note, the below values are not comparisons, but rather completely isolated and individual examples that happen to be categorized based on input types. This is because latency is affected by several things, some of which aren't always applicable to the scenario demonstrated.

To see prior numbers, please see this older page revision.

Measuring Latency

We've come up with a synchronous method of testing total system latency. We wrote a program that uses the on-board gpio's to control an ambient light sensor (Vishay Semiconductor Opto Division TEPT5700) and a bright blue LED. A camera would be pointed to the LED while a GStreamer pipeline would pipe it to some sink. Finally, the program controlling the LED and light sensor turns the LED on, measures how long it took the ambient light sensor to detect it, and repeat several times. If you would like to repeat our findings, please build the gw-latency-tester program and use in conjunction with the following hardware:

Vishay Semiconductor Opto Division TEPT5700
Bright Blue or White LED

Pinout to the DIO connector is as follows:

DIO0 - Power to the ambient light sensor (Collector Side), tie other end to DIO3
DIO1 - Power to the LED, tie other end to GND
DIO2 - [OPTIONAL] Status LED, tie other end to GND
DIO3 - Receiver end of ambient light sensor (Emitter Side), tie other end to DIO0
GND  -

Usage is as follows:

root@ventana:~# ./gw-latency-tester
gw-latency-tester <pwr_dio emit_dio led_dio recv_dio> [<count>] [<udelay>] [<alpha>]

   DIO:  0  1  2  3
         ----------
GW54xx:  9 19 41 42
GW53xx: 16 19 17 20
GW52xx: 16 19 17 20
GW51xx: 16 19 17 18
GW551x: Unsupported
GW552x: 16 19 17 20

The below results will show how the program was run, so please refer to them for examples.

In general (unless otherwise specified), we use the following displays configured in the following ways:

HDMI: Hanns-G HL273
- Resolution: 1920x1080p-60
- Manufacturer specified latency: 2ms
LVDS: HannStar HSD100PXN1
- Resolution: 1024x768p-60
- Manufacturer specified rise time latency: 3-6ms
- Manufacturer specified fall time latency: 9-18ms
CVBS: Generic 5" inch TFT LCD Monitor (AC-530DB)
- Resolution: D:720x480i-60

Accounting for Latency

When we say a system has a latency of 66ms, this number only accounts from end to end devices. However, if we know certain device latencies (such as a displays), we can subtract that off and get fine-tuned numbers.

Using the measurement method described above, calculating the circuitry involved RC time constants, LED Diode rise/fall times, and the response time of the ambient light sensor, we get a "circuitry latency" of: (sensor fall time response) + (led rise time response) == (2us + 13us) + (200ns + 13us) = 28.200us

Because of DIO levels, we'll round that number down to 28us. Plus add in latency from an input (let's assume a camera has exactly 1framerate of latency at 30fps) at 33ms, and finally add in the display latency (we'll assume 4ms). Adding these together produces a total of: 28us + 33ms + 4ms = 37.28ms of latency. We can now say that latency inherent to our product is 66ms - 37.28ms = 28.72ms.

Latency Summary Table

Here is a summary table of the below results.

Note that customers have reported down to 4ms latency on 1080p30 HDMI input to 1080p30 HDMI output eliminating the source (camera) latency. Note the GoPro has been reported to have 60-100ms of latency itself, however, this is unverified by Gateworks.

Loopback:

Type	Capture	Display	End-To-End Latency
Analog	CVBS(NTSC:480i@30fps) imxv4l2videosrc(IPU)	CVBS monitor imxg2dvideosink(GPU)	56ms
Analog	CVBS(NTSC:480i@30fps) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	66ms
Analog	CVBS(NTSC:480i@30fps) imxv4l2videosrc(IPU)	LVDS monitor imxg2dvideosink(GPU)	76ms

Analog	PCI-AVC8000(NTSC:480i@30fps) imxv4l2videosrc(IPU)	CVBS monitor imxg2dvideosink(GPU)	55ms
Analog	PCI-AVC8000(NTSC:480i@30fps) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	67ms
Analog	PCI-AVC8000(NTSC:480i@30fps) imxv4l2videosrc(IPU)	LVDS monitor imxg2dvideosink(GPU)	78ms

Digital	HDMI(GoPro:720p@60fps) imxv4l2videosrc(IPU)	CVBS monitor imxg2dvideosink(GPU)	92ms
Digital	HDMI(GoPro:720p@60fps) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	96ms
Digital	HDMI(GoPro:720p@60fps) imxv4l2videosrc(IPU)	LVDS monitor imxg2dvideosink(GPU)	117ms

Digital	HDMI(GoPro:480p@60) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	101ms
Digital	HDMI(GoPro:720p@30) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	113ms
Digital	HDMI(GoPro:960p@60) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	157ms
Digital	HDMI(GoPro:1080p@60) imxv4l2videosrc(IPU)	HDMI monitor imxg2dvideosink(GPU)	175ms

RTSP Streaming:

Capture	Transform	Encode(VPU)	Stream	Decode(VPU)	Display	End-To-End Latency
CVBS(NTSC:480i@30fps) yuv422smp imxv4l2videosrc(IPU)	imxipuvideotransform(IPU)	imxvpuenc_h264 3mbps CBR	RTSP latency=10ms	imxvpudec (h264)	HDMI monitor imxg2dvideosink(GPU)	98ms
PCI-AVC8000(NTSC:480i@30fps) yuv422smp imxv4l2videosrc(IPU)	imxipuvideotransform(IPU)	imxvpuenc_h264 3mbps CBR	RTSP latency=10ms	imxvpudec (h264)	HDMI monitor imxg2dvideosink(GPU)	98ms
HDMI(GoPro:720p@60fps) yuv422smp imxv4l2videosrc(IPU)	imxipuvideotransform(IPU)	imxvpuenc_h264 5.5mbps CBR	RTSP latency=10ms	imxvpudec (h264)	HDMI monitor imxg2dvideosink(GPU)	160ms

Notes:

imxipuvideosink and imxg2dvideosink have the same latencies.
LVDS display requires a transform from YUV to RGB colorspace.
HDMI capture using yuv422smp requires a transform before encoding while yuv422bt656 does not.
IPU transforms with a width or height greater than 1024 (720p/720i/1080p/1080i) require striping equating to two transforms

CVBS (Analog) In

Using a 208C Wired Micro Mini Camera with NTSC 720x480@30FPS output captured via the Ventana Analog in (adv7180 SDTV Video Decoder) with 8bit ITU-R BT656 output to the IMX6 CSI, the following latencies were found using a GW5400:

CVBS in to HDMI out

CVBS Input to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video1 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.082425s
Min Latency: 0.052815s
Max Jitter : 0.029610s
Exponential Moving Average (alpha=0.1): 0.065967s

CVBS in to LVDS out

CVBS Input to LVDS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video1 ! imxg2dvideosink framebuffer=/dev/fb4

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.082155s
Min Latency: 0.055859s
Max Jitter : 0.026296s
Exponential Moving Average (alpha=0.1): 0.076021s

CVBS in to CVBS out

CVBS Input to CVBS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video1 ! imxg2dvideosink framebuffer=/dev/fb2

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.066111s
Min Latency: 0.045768s
Max Jitter : 0.020343s
Exponential Moving Average (alpha=0.1): 0.056305s

CVBS in to RTSP out

RTSP is an audio/video streaming standard that is commonly supported by various player clients.

Notes:

RTSP RFC
Note that latency=0 on the receiver will get it to display frames as soon as it receives them. However, depending on network congestion/frame sizes, this could cause video stuttering due to varying latencies.
These tests were done through a ZyXEL GS1100-24 Switch with 4 ports having active traffic.
RTSP clients (players) will have a configuration that specifically adds latency by stream buffering to allow for audio/video synchronization which can be on the order of 10 to 1000ms. For gstreamer rtspsrc this is the 'latency' parameter - we set it to 10ms to minimize latency as a value of 0 can confuse gstreamer.
See the gstreamer/streaming page for more examples on RTSP streaming

The below sections show various gstreamer sinks running on a GW5304 running Yocto 1.8 and an Ubuntu based PC.

Yocto 1.8 GW5304

Receiver latency set to 10, bitrate set to 3mbit/s:

CVBS input to RTSP Server (gst-variable-rtsp-server)

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=10 ! \
 rtph264depay ! h264parse ! imxvpudec ! imxg2dvideosink

sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video1 -s imxv4l2videosrc -r 0 -b 3000
```

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.100264334s
Min Latency: 0.057308000s
Max Jitter : 0.042956334s
Exponential Moving Average (alpha=0.1): 0.092784375s

Here is an example of using udpsink instead of the gst-variable-rtsp-server application. Receiver latency set to 10, bitrate set to 3mbit/s:

CVBS input to RTSP Server (gst-variable-rtsp-server)

sender:

gst-launch-1.0 imxv4l2videosrc device=/dev/video3 ! \
 imxipuvideotransform ! imxvpuenc_h264 bitrate=3000 ! \
 rtph264pay ! udpsink host=172.24.10.63 port=9001

receiver:

gst-launch-1.0 udpsrc port=9001 \
 caps="application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264" ! \
 rtph264depay ! h264parse ! imxvpudec ! imxg2dvideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.116625333s
Min Latency: 0.083219333s
Max Jitter : 0.033406000s
Exponential Moving Average (alpha=0.1): 0.098617987s

Receiver latency set to 100, bitrate set to 3mbit/s:

CVBS input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video1 -s imxv4l2videosrc -r 0 -b 3000
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=100 ! \
 rtph264depay ! h264parse ! imxvpudec ! imxg2dvideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.166653334s
Min Latency: 0.131223333s
Max Jitter : 0.035430001s
Exponential Moving Average (alpha=0.1): 0.139983921s

Ubuntu 14.04 i5 Desktop PC

Receiver latency set to 10, bitrate set to 3mbit/s:

CVBS input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video1 -s imxv4l2videosrc -r 0 -b 3000
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=10 ! \
 decodebin ! autovideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.118248000s
Min Latency: 0.056305334s
Max Jitter : 0.061942666s
Exponential Moving Average (alpha=0.1): 0.081248197s

Receiver latency set to 100, bitrate set to 3mbit/s:

CVBS input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video1 -s imxv4l2videosrc -r 0 -b 3000
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=100 ! \
 decodebin ! autovideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.167262000s
Min Latency: 0.138012667s
Max Jitter : 0.029249333s
Exponential Moving Average (alpha=0.1): 0.164639100s

HDMI (Digital) In

This section is for boards using hdmi capture to various outputs. The in-depth results are based off of the GoPro Hero3 camera.

Please note that the camera itself is responsible for a lot of the latency. Here is an example of how various HDMI output devices can vary (using the same output format and capture format):

HDMI input (yuv422smp - Dino-Lite Digital Microscope @ 1280x720p@60) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.116650000s
Min Latency: 0.068762333s
Max Jitter : 0.047887667s
Exponential Moving Average (alpha=0.1): 0.109525081s

HDMI input (yuv422smp - Incredisonic Dash Cam @ 1280x720p@60) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.130328000s
Min Latency: 0.085225000s
Max Jitter : 0.045103000s
Exponential Moving Average (alpha=0.1): 0.117414606s

HDMI input (yuv422smp - GoPro Hero3 @ 1280x720p@60) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.115457666s
Min Latency: 0.095496333s
Max Jitter : 0.019961333s
Exponential Moving Average (alpha=0.1): 0.096331845s

As you can see, camera choice plays a huge factor in latency numbers. In this case, the GoPro had 20ms less latency than the Incredisonic Dash Cam, and 10ms less latency than the Dino-Lite Digital Microscope.

Also note that HDMI sources have variying latencies based on their output formats. For example 1080p@30 on the GoPro has increased latencies due it its own performance.

Here are some GoPro Hero3 latency numbers at different output modes:

HDMI input (yuv422smp - GoPro Hero3 @ 1080p@60) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.198507s
Min Latency: 0.167948s
Max Jitter : 0.030559s
Exponential Moving Average (alpha=0.1): 0.175236s

HDMI input (yuv422smp - GoPro Hero3 @ 960p@60) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.176905000s
Min Latency: 0.137760667s
Max Jitter : 0.039144333s
Exponential Moving Average (alpha=0.1): 0.156957710s

HDMI input (yuv422smp - GoPro Hero3 @ 720p@30) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.138299333s
Min Latency: 0.096406667s
Max Jitter : 0.041892666s
Exponential Moving Average (alpha=0.1): 0.112956985s

HDMI input (yuv422smp - GoPro Hero3 @ 480p@60) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.116750333s
Min Latency: 0.093424667s
Max Jitter : 0.023325666s
Exponential Moving Average (alpha=0.1): 0.101177281s

Also note that any resolution larger than 1080x720 (720p/720i) requires striping for any IPU transform that needs to be performed on the IMX (ie colorspace transform for encoding when capturing in yuv422smp mode and output transform when displaying on a device that differs in format).

HDMI in to HDMI out

With the GoPro configured to output 1280x720p@60, pixel format YUV420, the following latencies were found using a GW5400:

While capturing in yuv422smp:

HDMI input (yuv422smp - GoPro Hero3) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.115457666s
Min Latency: 0.095496333s
Max Jitter : 0.019961333s
Exponential Moving Average (alpha=0.1): 0.096331845s

While capturing in bt656:

HDMI input (yuv422bt656 - GoPro Hero3) to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb0

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.113161667s
Min Latency: 0.085511333s
Max Jitter : 0.027650334s
Exponential Moving Average (alpha=0.1): 0.097953780s

HDMI in to LVDS out

While capturing in yuv422smp:

HDMI input (yuv422smp - GoPro Hero3) to LVDS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb4

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.127060667s
Min Latency: 0.106143666s
Max Jitter : 0.020917001s
Exponential Moving Average (alpha=0.1): 0.117725942s

While capturing in bt656:

HDMI input (yuv422bt656 - GoPro Hero3) to LVDS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb4

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.173456000s
Min Latency: 0.120619667s
Max Jitter : 0.052836333s
Exponential Moving Average (alpha=0.1): 0.131980293s

HDMI in to CVBS out

While capturing in yuv422smp:

HDMI input (yuv422smp - GoPro Hero3) to CVBS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb2

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.103408000s
Min Latency: 0.091112000s
Max Jitter : 0.012296000s
Exponential Moving Average (alpha=0.1): 0.092611801s

While capturing in bt656:

HDMI input (yuv422bt656 - GoPro Hero3) to CVBS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video0 ! imxg2dvideosink framebuffer=/dev/fb2

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.114230334s
Min Latency: 0.099739667s
Max Jitter : 0.014490667s
Exponential Moving Average (alpha=0.1): 0.100241924s

HDMI in to RTSP out

RTSP is an audio/video streaming standard that is commonly supported by various player clients.

Notes:

RTSP RFC
Note that latency=0 on the receiver will get it to display frames as soon as it receives them. However, depending on network congestion/frame sizes, this could cause video stuttering due to varying latencies.
These tests were done through a ZyXEL GS1100-24 Switch with 4 ports having active traffic.
RTSP clients (players) will have a configuration that specifically adds latency by stream buffering to allow for audio/video synchronization which can be on the order of 10 to 1000ms. For gstreamer rtspsrc this is the 'latency' parameter - we set it to 10ms to minimize latency as a value of 0 can confuse gstreamer.
See the gstreamer/streaming page for more examples on RTSP streaming

The below sections show various gstreamer sinks running on a GW5304 running Yocto 1.8 and an Ubuntu based PC.

Yocto 1.8 GW5304

Receiver latency set to 10, bitrate set to 5.5mbit/s:

HDMI input (yuv422smp - GoPro Hero3) to HDMI Output
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video0 -s imxv4l2videosrc -r 0 -b 5500
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=10 ! \
 rtph264depay ! h264parse ! imxvpudec ! imxg2dvideosink

latency:

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.183257333s
Min Latency: 0.149575667s
Max Jitter : 0.033681666s
Exponential Moving Average (alpha=0.1): 0.160407397s

Ubuntu 14.04 i5 Desktop PC

Receiver latency set to 10, bitrate set to 5.5mbit/s:

HDMI input (yuv422smp - GoPro Hero3) to HDMI Output
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video0 -s imxv4l2videosrc -r 0 -b 5500
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=10 ! \
 decodebin ! autovideosink

latency:

gw-latency-tester 9 19 41 42 60
=== Summary ===
Ran 60 times
Max Latency: 0.127060667s
Min Latency: 0.106143666s
Max Jitter : 0.020917001s
Exponential Moving Average (alpha=0.1): 0.117725942s

avc8000nano (miniPCIe capture card) in

This section is for boards using the avc8000nano miniPCIe capture card to various outputs.

avc8000nano in to HDMI out

avc8000nano Input to HDMI Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video3 ! imxg2dvideosink framebuffer=/dev/fb0

latency:

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.067630s
Min Latency: 0.058137s
Max Jitter : 0.009493s
Exponential Moving Average (alpha=0.1): 0.066845s

avc8000nano in to LVDS out

avc8000nano Input to LVDS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video3 ! imxg2dvideosink framebuffer=/dev/fb4

latency:

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.090251s
Min Latency: 0.059275s
Max Jitter : 0.030976s
Exponential Moving Average (alpha=0.1): 0.078264s

avc8000nano in to CVBS out

avc8000nano Input to CVBS Output

gst-launch-1.0 imxv4l2videosrc device=/dev/video3 ! imxg2dvideosink framebuffer=/dev/fb2

latency:

gw-latency-tester 9 19 41 42 60 0
=== Summary ===
Ran 60 times
Max Latency: 0.062595s
Min Latency: 0.049624s
Max Jitter : 0.012971s
Exponential Moving Average (alpha=0.1): 0.055531s

avc8000nano in to RTSP out

RTSP is an audio/video streaming standard that is commonly supported by various player clients.

Notes:

RTSP RFC
Note that latency=0 on the receiver will get it to display frames as soon as it receives them. However, depending on network congestion/frame sizes, this could cause video stuttering due to varying latencies.
These tests were done through a ZyXEL GS1100-24 Switch with 4 ports having active traffic.
RTSP clients (players) will have a configuration that specifically adds latency by stream buffering to allow for audio/video synchronization which can be on the order of 10 to 1000ms. For gstreamer rtspsrc this is the 'latency' parameter - we set it to 10ms to minimize latency as a value of 0 can confuse gstreamer.
See the gstreamer/streaming page for more examples on RTSP streaming

The below sections show various gstreamer sinks running on a GW5304 running Yocto 1.8 and an Ubuntu based PC.

Yocto 1.8 GW5304

Receiver latency set to 10, bitrate set to 3mbit/s:

avc8000nano input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video3 -s imxv4l2videosrc -r 0 -b 3000
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=10 ! \
 rtph264depay ! h264parse ! imxvpudec ! imxg2dvideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.116920334s
Min Latency: 0.059414667s
Max Jitter : 0.057505667s
Exponential Moving Average (alpha=0.1): 0.098957740s

Receiver latency set to 100, bitrate set to 3mbit/s:

avc8000nano input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video3 -s imxv4l2videosrc -r 0 -b 3000 
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=100 ! \
 rtph264depay ! h264parse ! imxvpudec ! imxg2dvideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.166873667s
Min Latency: 0.039013333s
Max Jitter : 0.127860334s
Exponential Moving Average (alpha=0.1): 0.156437334s

Ubuntu 14.04 i5 Desktop PC

Receiver latency set to 10, bitrate set to 3mbit/s:

avc8000nano input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video3 -s imxv4l2videosrc -r 0 -b 3000
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=10 ! \
 decodebin ! autovideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.129218s
Min Latency: 0.067037s
Max Jitter : 0.062181s
Exponential Moving Average (alpha=0.1): 0.091255s

Receiver latency set to 100, bitrate set to 3mbit/s:

avc8000nano input to RTSP Server (gst-variable-rtsp-server)
sender: (imxv4l2videosrc ! imxipuvideotransform ! imxvpuenc_h264 ! rtph264pay pt=96)
```
gst-variable-rtsp-server -i /dev/video3 -s imxv4l2videosrc -r 0 -b 3000
```

receiver:

gst-launch-1.0 rtspsrc location=rtsp://172.24.10.180:9099/stream latency=100 ! \
 decodebin ! autovideosink

latency:

gw-latency-tester 9 19 41 42 60 500000
=== Summary ===
Ran 60 times
Max Latency: 0.201775s
Min Latency: 0.165823s
Max Jitter : 0.035952s
Exponential Moving Average (alpha=0.1): 0.177493s

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