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tutorials: gstreamer tools: fix broken webm to ogg transcode pipeline

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The pipeline would error out with not-negotiated. Reason is that
the webm file doesn't have an average frame duration set in the
headers, so matroskademux outputs framerate=0/1, but theora in
Ogg really requires a fixed framerate, so that errors out.

Change example to H.264/AAC in MP4, which is more useful.

Fixes https://gitlab.freedesktop.org/gstreamer/gst-docs/-/issues/108

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7859>
This commit is contained in:
Tim-Philipp Müller 2024-11-09 17:05:18 +00:00 committed by GStreamer Marge Bot
parent 74d75e481c
commit 4702cae7ff
1 changed files with 8 additions and 3 deletions
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subprojects/gst-docs/markdown/tutorials/basic/gstreamer-tools.md
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@ -235,11 +235,16 @@ gst-launch-1.0 souphttpsrc location=https://gstreamer.freedesktop.org/data/media
A transcoding pipeline, which opens the webm container and decodes both
streams (via uridecodebin), then re-encodes the audio and video branches
with a different codec, and puts them back together in an Ogg container
(just for the sake of it).
with different codecs (H.264 + AAC), and puts them back together into an
MP4 container (just for the sake of it). Because of the way the x264enc
encoder behaves by default (consuming multiple seconds of video input before
outputtingi anything), we have to increase the size of the queue in the audio
branch to make sure the pipeline can preroll and start up. Another solution
would be to use `x264enc tune=zerolatency` but that results in lower quality
and is more suitable for live streaming scenarios.
```
gst-launch-1.0 uridecodebin uri=https://gstreamer.freedesktop.org/data/media/sintel_trailer-480p.webm name=d ! queue ! videoconvert ! theoraenc ! oggmux name=m ! filesink location=sintel.ogg d. ! queue ! audioconvert ! audioresample ! flacenc ! m.
gst-launch-1.0 uridecodebin uri=https://gstreamer.freedesktop.org/data/media/sintel_trailer-480p.webm name=d ! queue ! videoconvert ! x264enc ! video/x-h264,profile=high ! mp4mux name=m ! filesink location=sintel.mp4 d. ! queue max-size-time=5000000000 max-size-bytes=0 max-size-buffers=0 ! audioconvert ! audioresample ! voaacenc ! m.
```
A rescaling pipeline. The `videoscale` element performs a rescaling