GStreamer¶

GStreamer is a library for constructing graphs of media-handling components. This package provides the GStreamer core along with the base, good, bad and ugly plugin sets, the libav plugin and the RTSP server library, for use from the command line or by other packages.

Commands are located in /var/packages/gstreamer/target/bin and linked into /usr/local/bin:

gst-launch-1.0 - build and run a pipeline
gst-inspect-1.0 - list plugins and elements, show element details
gst-discoverer-1.0 - show media file information
gst-play-1.0 - play back media files
gst-typefind-1.0 - detect media types

ls -l /usr/local/bin/gst-*
# gst-launch-1.0 -> /var/packages/gstreamer/target/bin/gst-launch-1.0
# ...

Note

A non-interactive ssh command does not have /usr/local/bin in its PATH on DSM. Use the full path, or export PATH=/usr/local/bin:$PATH first.

Package Information¶

Property	Value
Package Name	gstreamer
Maintainer	@th0ma7
Upstream	gstreamer.freedesktop.org
License	LGPLv2.1 (GPL plugins enabled)
Dependencies	FFmpeg 8 (`libav` plugin), SynoCli Video Driver (x64, `va` plugin)

The libav plugin uses the libraries of the FFmpeg 8 package, which is installed alongside. Both must come from the same build: if gst-inspect-1.0 -b lists a blacklisted plugin, update FFmpeg 8 (see Troubleshooting).

Plugins¶

On x64 with DSM 7, gst-inspect-1.0 reports 199 plugins and about 1250 elements.

Purpose	Elements
Video decoding	`avdec_*` (FFmpeg: MPEG-2, MPEG-4, VC-1, ...), `openh264dec`, `libde265dec`, `av1dec` (aom), `vp8dec`/`vp9dec`
Video encoding	`x264enc`, `x265enc`, `openh264enc`, `av1enc` (aom), `svtav1enc` (64-bit), `vp8enc`/`vp9enc`, `avenc_*`
Audio	`fdkaacenc`/`fdkaacdec`, `lamemp3enc`, `mpg123audiodec`, `flacenc`/`flacdec`, `opusenc`/`opusdec`, `vorbisenc`/`vorbisdec`, `avdec_ac3`, `avdec_dca`, ...
Containers	`qtdemux`/`mp4mux`, `matroskademux`/`matroskamux`, `tsdemux`/`mpegtsmux`, ...
Streaming	`hlsdemux`, `hlssink2`, `dashdemux`, `srtsrc`/`srtsink`, `rtspsrc`, `rtspclientsink`
Capture	`v4l2src`, `dvbsrc`
Hardware (x64)	`vah264dec`, `vah265dec`, `vampeg2dec`, `vah264enc`, `vah265enc`, `vapostproc`, ... (see Hardware Acceleration)

# All plugins and elements
gst-inspect-1.0

# Details of one element (properties, supported formats)
gst-inspect-1.0 x264enc

Usage¶

# Inspect a media file
gst-discoverer-1.0 /volume1/video/movie.mkv

# Transcode any input to H.264/AAC in MP4 on the CPU
gst-launch-1.0 -e filesrc location=input.mkv ! decodebin name=d \
    d. ! queue ! videoconvert ! x264enc speed-preset=veryfast bitrate=4000 ! h264parse ! mp4mux name=m ! filesink location=output.mp4 \
    d. ! queue ! audioconvert ! audioresample ! fdkaacenc ! m.

decodebin picks the decoder for each stream: the hardware one when it can use it, otherwise the software one. TV recordings in MPEG-2 video and AC-3 audio are decoded by vampeg2dec (or avdec_mpeg2video) and avdec_ac3.

VideoStation seek options¶

gst-launch-1.0 carries the Synology VideoStation extensions that start a pipeline at a given position, once it is prerolled:

-s, --seek=TIME - flushing seek to TIME (seconds)
-S, --seek-no-flush=TIME - same, without flushing

# Play from 15 s
gst-launch-1.0 -s 15 filesrc location=input.mp4 ! decodebin ! fakesink sync=true

User Permissions¶

To use the GPU, your user must be a member of the videodriver group. Without it, the va plugin loads but exposes no element, and decodebin falls back to software decoding.

sudo synogroup --memberadd videodriver $(whoami)
# Log out and back in, then check:
id
# uid=1030(<username>) gid=100(users) groups=100(users),101(administrators),937(videodriver)

See FFmpeg: User Permissions for details.

Hardware Acceleration¶

On Intel-based models, VA-API accelerated elements are provided by the va plugin, using the drivers from the SynoCli Video Driver package, installed as a dependency.

Validate the VA-API elements¶

gst-inspect-1.0 va
# Output on an Intel Celeron J3455 (Gen9, DS918+):
#   vah264dec: VA-API H.264 Decoder in Intel(R) Gen Graphics
#   vah264enc: VA-API H.264 Encoder in Intel(R) Gen Graphics
#   vah265dec: VA-API H.265 Decoder in Intel(R) Gen Graphics
#   vah265enc: VA-API H.265 Encoder in Intel(R) Gen Graphics
#   vampeg2dec: VA-API Mpeg2 Decoder in Intel(R) Gen Graphics
#   vapostproc: VA-API Video Postprocessor in Intel(R) Gen Graphics
#   vadeinterlace, vacompositor, vajpegdec/enc, vavp8dec/enc, vavp9dec, ...

The list depends on the GPU. An empty list means the user cannot access the GPU (see User Permissions); vainfo from the video driver package shows what the driver itself supports (see FFmpeg: Hardware Acceleration).

Transcode on the GPU¶

# Decode, scale to 720p and encode on the GPU; audio on the CPU
gst-launch-1.0 -e filesrc location=input.mkv ! decodebin name=d \
    d. ! queue ! vapostproc ! "video/x-raw(memory:VAMemory),width=1280,height=720" ! vah264enc bitrate=2500 ! h264parse ! mp4mux name=m ! filesink location=output.mp4 \
    d. ! queue ! audioconvert ! audioresample ! fdkaacenc ! m.

Hardware decoders only accept what the GPU supports: an H.264 High 4:4:4 or an MPEG-2 4:2:2 stream is not linked to vah264dec/vampeg2dec. With decodebin the software decoder takes over; with an explicit vah264dec the pipeline stops with not-linked.

Performance Comparison (CPU vs GPU)¶

Measured on a DS918+ (Intel Celeron J3455, 4 cores, DSM 7.4):

Pipeline	Input	Time	FPS	Relative to CPU
CPU `avdec_h264` → `x264enc` (veryfast)	20 s H.264 1080p30	25.5 s	24	baseline
GPU `vah264dec` → `vah264enc`	same	4.0 s	150	~6× faster
GPU `vah264dec` → `vah265enc`	same	21.8 s	28	~1.2× faster
CPU decode, scale 720p → `x264enc`	same	13.1 s	46	baseline
GPU decode, `vapostproc` 720p → `vah264enc`	same	2.6 s	231	~5× faster
CPU `decodebin` → `x264enc` + `fdkaacenc`	60 s MPEG-2/AC-3 576p25	29.8 s	50	baseline
GPU `decodebin` → `vah264enc` + `fdkaacenc`	same	6.2 s	242	~5× faster

H.265 encoding on this GPU gains little over the CPU; H.264 is the format to favour for real-time transcoding.

Note

The legacy gstreamer-vaapi plugins (vaapih264dec, ...) were removed upstream in GStreamer 1.28 in favor of the va plugin. The OpenMAX wrapper (gst-omx), discontinued upstream after 1.22, is not provided.

Troubleshooting¶

Plugin not found or blacklisted¶

GStreamer caches its plugin registry in ~/.cache/gstreamer-1.0/. After a package upgrade, remove the cache so plugins are rescanned:

rm -rf ~/.cache/gstreamer-1.0
gst-inspect-1.0 > /dev/null

A plugin that fails to load is blacklisted. List them, then load one directly to see why:

gst-inspect-1.0 -b
gst-inspect-1.0 /var/packages/gstreamer/target/lib/gstreamer-1.0/libgsthls.so
# Could not load plugin file: ... libnettle.so.9: cannot open shared object file

A missing library that FFmpeg 8 provides (as libnettle above) means FFmpeg 8 and GStreamer come from different builds: update FFmpeg 8.

Debugging a pipeline¶

Use GST_DEBUG to get more information on a failing pipeline:

GST_DEBUG=3 gst-launch-1.0 ...

Using GStreamer in a package¶

A package that builds against GStreamer depends on its cross packages, for example cross/gstreamer and cross/gst-plugins-base. GStreamer itself takes the FFmpeg libraries for gst-libav from the FFmpeg meta package:

FFMPEG_PACKAGE = ffmpeg8
include ../../mk/spksrc.spk-meta.mk

Architecture Support¶

Architecture	DSM 6	DSM 7	Notes
x64	✓	✓	VA-API hardware acceleration
aarch64	✓	✓
armv7	✓	✓
i686 (evansport)	✓	✓	No `dvb` (Linux 3.2 headers)
comcerto2k	-	✓	No `dvb` (Linux 3.2 headers)
ppc (qoriq)	✓	-	No `openh264`
armv5, hi3535	-	-	Compiler too old (gcc < 4.9)

On DSM 6 and comcerto2k (gcc 4.9), the taglib plugin (C++17) is not built.