From 4702cae7ff874e253d64351ace3baf13c4432bba Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Tim-Philipp=20M=C3=BCller?= <tim@centricular.com> Date: Sat, 9 Nov 2024 17:05:18 +0000 Subject: [PATCH] tutorials: gstreamer tools: fix broken webm to ogg transcode pipeline 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> --- .../markdown/tutorials/basic/gstreamer-tools.md | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/subprojects/gst-docs/markdown/tutorials/basic/gstreamer-tools.md b/subprojects/gst-docs/markdown/tutorials/basic/gstreamer-tools.md index 461aea0d75..831212b60d 100644 --- a/subprojects/gst-docs/markdown/tutorials/basic/gstreamer-tools.md +++ b/subprojects/gst-docs/markdown/tutorials/basic/gstreamer-tools.md @@ -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