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FFmpeg

Building FFmpeg with SRT

FFmpeg supports the SRT protocol out of the box. To include SRT, FFmpeg project should be built with the configure flag --enable-libsrt. Refer to FFmpeg's Compilation Guide for the detailed build instructions for a particular platform.

Please check Quickstart: Running SRT and FFmpeg on Ubuntu YouTube Video for additional instructions.

Note

There is a feedback that SRT cannot be built by FFmpeg if both --enable-libsrt and --enable-shared options are specified.

A list of available protocols can be determined by calling ffmpeg -protocols. "srt" (or "libsrt") should be listed as both input and output protocol.

General Usage

Once SRT is available, an SRT output can be specified like this:

"srt://<destination_ip>:<destination_port>"

Note

Note that FFmpeg expects SRT latency to be specified in microseconds, not milliseconds as it's done in the SRT library. The following URI sets the SRT latency to be 400 milliseconds: srt://<ip>:<port>?latency=400000.

It's recommended to use MPEG-TS as a container: -f mpegts.

ffplay should be able to play SRT streaming with ffplay srt://<ip>:<port>.

Piping can be done like this:

srt-live-transmit srt://<ip>:<port> file://con | ffplay -f mpegts -

Please take into account issue #407.

Or pipe via UDP socket on a localhost:

srt-live-transmit srt://<ip>:<port> udp://127.0.0.1:<portB>
ffplay udp://127.0.0.1:<portB> -f mpegts

In the latest case the -f mpegts argument is optional.

Note

-re option will slow down the reading:
"Read input at native frame rate. Mainly used to simulate a grab device, or live input stream (e.g. when reading from a file). Should not be used with ... live input streams (where it can cause packet loss). By default ffmpeg attempts to read the input(s) as fast as possible. This option will slow down the reading of the input(s) to the native frame rate of the input(s). It is useful for real-time output (e.g. live streaming)".

Examples

FFmpeg example: Grabbing X11 desktop screen and streaming to SRT

ffmpeg -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 \
       -f mpegts srt://<target_ip>:<target_port>

FFmpeg example with SMPTE bars test video source

ffmpeg -f lavfi -re -i smptebars=duration=60:size=1280x720:rate=30 -f lavfi -re \
       -i sine=frequency=1000:duration=60:sample_rate=44100 -pix_fmt yuv420p \
       -c:v libx264 -b:v 1000k -g 30 -keyint_min 120 -profile:v baseline \
       -preset veryfast -f mpegts "srt://127.0.0.1:4200?pkt_size=1316"

FFmpeg example: RTSP to SRT

ffmpeg -i rtsp://<src_rtsp_uri> -c copy -f mpegts srt://<target_srt_uri>

See also rtsp2srt project.

Example with FFmpeg and srt-live-transmit test application

Send to UDP localhost port 5000:

ffmpeg -f lavfi -re -i smptebars=duration=60:size=1280x720:rate=30 -f lavfi -re \
       -i sine=frequency=1000:duration=60:sample_rate=44100 -pix_fmt yuv420p \
       -c:v libx264 -b:v 1000k -g 30 -keyint_min 120 -profile:v baseline \
       -preset veryfast -f mpegts "udp://127.0.0.1:5000?pkt_size=1316"

Transmit from UDP to SRT destination:

./srt-live-transmit udp://:5000 srt://<ip>:<port>?mode=rendezvous

Receive with SRT:

./srt-live-transmit srt://<ip>:<port>?mode=rendezvous file://con > ./received.ts

Receive SRT and pass to /dev/nul:

`./ffmpeg -i srt://<ip>:<port> -f null /dev/null`
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