GstRTMPMetadata examples Using gst-launch

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RidgeRun GstRTMPMetadata

Table of Contents [Sticky]

• GstRTMPMetadata Basics
• Getting Started
  • Evaluating the project
  • Getting the code
  • Building the project
• User Guide
• Examples
  • Using gst-launch
  • Using Gstd
  • C Example
• FAQ
• Contact Us

Inserting metadata

This subsection presents sample pipelines to insert and extract arbitrary metadata over RTMP/FLV using the patched flvmux / flvdemux. The metadata is carried inside FLV Script Data tags and can be injected via properties (e.g., meta-string) or binary payloads (meta-binary). Extraction can attach a GstMeta to outgoing buffers and/or emit a signal with the payload.

Step 1 – Start a local RTMP server

You can quickly spin up a local RTMP server using SRS:

docker run --rm -p 1935:1935 ossrs/srs

Step 2 – Run the sender pipeline (insertion)

The following sender pipeline encodes a color bar test source (H.264) and injects the metadata string "Hello RTMP Metadata" into the FLV stream via flvmux meta-string=.... Finally, it pushes the stream to the local RTMP server.

gst-launch-1.0 -e \
  videotestsrc is-live=true pattern=smpte ! video/x-raw,framerate=30/1 ! \
  x264enc tune=zerolatency speed-preset=ultrafast key-int-max=60 byte-stream=false ! \
  video/x-h264,stream-format=avc,alignment=au ! \
  flvmux name=mux streamable=true meta-string="Hello RTMP Metadata" ! \
  rtmpsink location="rtmp://127.0.0.1/live/test"

Step 3 – Run the receiver pipeline (extraction)

On the receiver side, the following pipeline pulls the RTMP stream, demuxes FLV, and enables both:

• attach-flvmeta=true – attaches the extracted metadata as a GstMeta on outgoing buffers, and
• flv-meta-signal=true – emits a signal with the payload as GBytes for immediate application handling.

GST_DEBUG=flv*:6,flvdemux:6,gstflv*:6 \
gst-launch-1.0 -m \
  rtmpsrc location="rtmp://127.0.0.1/live/test" ! \
  flvdemux attach-flvmeta=true flv-meta-signal=true name=d \
    d.video ! identity silent=false ! fakesink sync=false \
    d.audio ! fakesink sync=false

Step 4 – Check the output

In the console you should observe bus messages and debug logs from flvdemux indicating that metadata Script Data has been parsed. When flv-meta-signal=true is set, the element emits a flv-meta signal carrying the metadata payload as GBytes. When attach-flvmeta=true is set, the first audio/video buffers downstream include a custom GstMeta with the same payload.

0:00:00.468534452 121718 0x55a34b45a8c0 INFO                flvdemux gstflvdemux.c:499:gst_flv_demux_parse_metadata_item:<d> Meta-string: Hello RTMP Metadata

Notes

• You can inject metadata multiple times by setting meta-string more than once during streaming.
• For binary payloads (e.g., structured blobs), use meta-binary instead of meta-string on flvmux.
• This support is provided as patches to flvmux and flvdemux and is available for GStreamer 1.16.x, 1.20.x, and 1.24.x.

Troubleshooting

• If you do not see metadata logs on the receiver:
  • Ensure the sender used meta-string/meta-binary on flvmux.
  • Verify caps: video/x-h264, stream-format=avc, alignment=au before flvmux.
  • Increase debug: GST_DEBUG=flv*:6,flvdemux:6,gstflv*:6 -m.
• On headless systems, use fakesink or identity silent=false branches to inspect buffer flow.
• If your RTMP server requires a different app/stream path, adjust rtmpsink location=rtmp://<host>/<app>/<stream>.

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