# rtprtxqueue

rtprtxqueue maintains a queue of transmitted RTP packets, up to a configurable limit (see max-size-time, max-size-packets), and retransmits them upon request from the downstream rtpsession (GstRTPRetransmissionRequest event).

This element is similar to rtprtxsend, but it has differences:

- Retransmission from rtprtxqueue is not RFC 4588 compliant. The retransmitted packets have the same ssrc and payload type as the original stream.
- As a side-effect of the above, rtprtxqueue does not require the use of rtprtxreceive on the receiving end. rtpjitterbuffer alone is able to reconstruct the stream.
- Retransmission from rtprtxqueue happens as soon as the next regular flow packet is chained, while rtprtxsend retransmits as soon as the retransmission event is received, using a helper thread.
- rtprtxqueue can be used with rtpbin without the need of hooking to its request-aux-sender signal, which means it can be used with rtpbin using gst-launch.

See also rtprtxsend, rtprtxreceive

# Example pipelines

     gst-launch-1.0 rtpbin name=b rtp-profile=avpf \
        audiotestsrc is-live=true ! opusenc ! rtpopuspay pt=96 ! rtprtxqueue ! b.send_rtp_sink_0 \
        b.send_rtp_src_0 ! identity drop-probability=0.01 ! udpsink host="127.0.0.1" port=5000 \
        udpsrc port=5001 ! b.recv_rtcp_sink_0 \
        b.send_rtcp_src_0 ! udpsink host="127.0.0.1" port=5002 sync=false async=false

Sender pipeline

     gst-launch-1.0 rtpbin name=b rtp-profile=avpf do-retransmission=true \
        udpsrc port=5000 caps="application/x-rtp,media=(string)audio,clock-rate=(int)48000,encoding-name=(string)OPUS,payload=(int)96" ! \
            b.recv_rtp_sink_0 \
        b. ! rtpopusdepay ! opusdec ! audioconvert ! audioresample ! autoaudiosink \
        udpsrc port=5002 ! b.recv_rtcp_sink_0 \
        b.send_rtcp_src_0 ! udpsink host="127.0.0.1" port=5001 sync=false async=false

Receiver pipeline

## Hierarchy

    GObject
        ╰──GInitiallyUnowned
            ╰──GstObject
                ╰──GstElement
                    ╰──rtprtxqueue

## Factory details

Authors: – Wim Taymans

Classification: – `Codec`

Rank – none

Plugin – rtpmanager

Package – GStreamer Good Plug-ins

## Pad Templates

### `sink`

    application/x-rtp:

Presence – always

Direction – sink

Object type – GstPad

### `src`

    application/x-rtp:

Presence – always

Direction – src

Object type – GstPad

## Properties

### fulfilled-requests

    “fulfilled-requests” guint

Number of fulfilled retransmission requests

Flags : Read

Default value : 0

### max-size-packets

    “max-size-packets” guint

Amount of packets to queue (0 = unlimited)

Flags : Read / Write

Default value : 100

### max-size-time

    “max-size-time” guint

Amount of ms to queue (0 = unlimited)

Flags : Read / Write

Default value : 0

### requests

    “requests” guint

Total number of retransmission requests

Flags : Read

Default value : 0

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