Problem sending high-bandwidth raw video over localhost UDP

[Michael Franzl]

Hello,

I'm trying to send 1280 x 720 @ 30fps BGRA video via rtpvrawpay and
udpsink from one gst-launch process to another on the same machine, but
I'm seeing visual artefacts on the receiver which suggest to me that
there could be packets lost (due to bandwidth?), or memory issues.

The sender:

> gst-launch-1.0 -v \
> videotestsrc pattern=ball flip=1 is-live=1 ! \
> video/x-raw,format=BGRA,width=1280,height=720,pixel-aspect-ratio=1/1,interlace-mode=progressive,framerate=30/1 ! \
> rtpvrawpay ! queue ! udpsink host=127.0.0.1 port=50000


The receiver:

> gst-launch-1.0 -v \
> udpsrc port=50000 caps="application/x-rtp,clock-rate=90000,encoding-name=RAW,sampling=(string)BGRA,width=(string)1280,height=(string)720" ! queue ! rtpvrawdepay ! videoconvert ! autovideosink


I'm attaching a screenshot of the receiving window, showing the type of
visual artefacts I mean (I hope the attachment comes through).

I calculate the bandwidth to 1280 x 720 x 32 bits x 30fps = 884
MBit/sec. Localhost *should* be able to handle this, but since that goes
through the Linux kernel, I don't know exactly.

I'm seeing the same problem on a wide range of machines (8 year old
Laptop to brand-new Intel Kaby Lake architecture desktop machine), and
from Gstreamer 1.10 to a very recent git version.

Tweaking MTU size and chunks-per-frame on rtpvrawpay changes the
artefact size and frequency but doesn't eradicate them. There is a small
hint that it *could* be Gstreamer. The following ...

> gst-launch-1.0 -v videotestsrc pattern=ball is-live=1 ! video/x-raw,format=AYUV,width=1280,height=720,pixel-aspect-ratio=1/1,interlace-mode=progressive,framerate=30/1 ! rtpvrawpay mtu=65000 chunks-per-frame=100 ! fakesink

... gives an exception ...

> (gst-launch-1.0:26037): GLib-ERROR **: /build/glib2.0-B1uXKV/glib2.0-2.50.3/./glib/gmem.c:100: failed to allocate 34359738456 bytes
> Trace/breakpoint trap

Any hints appreciated,

Thanks,
Michael
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