Due to the use of DeepStream This framework , I can't get around it gstreamer-1.0, So I learned the usage of this framework during this time . Not able to read the source code .gstreamer In the frame ,gst-inspect-1.0 and gst-launch-1.0 These two tools must be familiar with , Now gst-launcher-1.0 Take notes of the usage of , So as not to forget . Reference resources https://blog.csdn.net/u010168781/article/details/102805210

One 、 Command format

gst-launch-1.0 [OPTIONS] PIPELINE-DESCRIPTION

1. Parameter options

• -help
• -v, --verbose
• -q, --quiet Don't print information
• -m, --messages Output messages on the pipeline bus
• -t, --tags Output flag tag（ Also known as metadata ）
• -o FILE, --output=FILE Save pipe to XML In file , And exit
• -f, --no_fault Do not install fault handlers
• -T, --trace Print memory allocation tracking . This feature must be enabled at compile time to work .

2. Pipe description string

• Components ： ELEMENTTYPE [PROPERTY1 …]
• Component properties ：PROPERTY=VALUE …, Use spaces between multiple values
• The box Bin： [BINTYPE.] ([PROPERTY1 …] PIPELINE-DESCRIPTION), Usually in gst_parse_launch() Use in a function , Build part of the pipeline , Not a complete top-level pipeline
• link Link：[[SRCELEMENT].[PAD1,…]] ! [[SINKELEMENT].[PAD1,…]], take SRCELEMENT adopt “!” link to SINKELEMENT
  [[SRCELEMENT].[PAD1,…]] ! CAPS ! [[SINKELEMENT].[PAD1,…]],CAPS Indicates filter , Links match CAPS Of PAD
  Ability CAP：MIMETYPE [, PROPERTY[, PROPERTY …]]] [; CAPS[; CAPS …]], Using the given mimetype And optional given attribute creation function .
  Ability attributes ：NAME=[(TYPE)] VALUE in lists and ranges: [(TYPE)] VALUE

Two 、 Use cases

1. Play MP4 Audio and video

MP4 Documents usually have 2 A flow ： Audio and video streams , Some files will have subtitle streams . Usually we only deal with 2 One stream is enough . The general video stream adopts h264 code , The audio stream adopts aac code . At first, because I was not familiar with gst-inspect Usage of , As a result, the audio and video decoder cannot find , A lot of time was wasted .

gst-inspect-1.0 | grep h264 find h264 decoder avdec_h264

gst-inspect-1.0 | grep aac find aac decoder avdec_aac. It can also be used. faad decode ,faad Output is 16 Bit audio ,avdec_aac Output is 32 Bit audio

gst-launch-1.0 About China demux I've been groping for a long time ,mp4 Documents need to use qtdemux(quick time demux), use names Property separation pipeline , The correct usage is as follows

Play the video

gst-launch-1.0 filesrc location=gongye.mp4 ! qtdemux name=demuxer demuxer. ! avdec_h264 ! xvimagesink

Play the audio (audioresample Optional )

gst-launch-1.0 filesrc location=gongye.mp4 ! qtdemux name=demuxer demuxer. ! avdec_aac ! audioconvert ! audioresample ! alsasink  

Play audio and video

gst-launch-1.0 filesrc location=gongye.mp4 ! qtdemux name=demuxer demuxer. ! queue ! avdec_aac ! audioconvert ! alsasink demuxer. ! queue ! avdec_h264 ! xvimagesink  

demuxer. The stream name can be specified later , Such as demuxer.video_0,demuxer.audio_0, The stream name must correspond to the stream name in the file .

Other file formats , Such as flv,ogg,mpeg And other documents can be used in a similar way , First use gst-inspect-1.0 Find the corresponding demux And audio and video decoder , Then build the pipeline and play immediately .

For... In components request pad,gst-launch-1.0 You can also specify request pad The connection of , Typical as tee,nvstreammux And other components need request pad, The connection is as follows ：

gst-launch-1.0 filesrc location=sample_720.h264 ! h264parse ! nvv4l2decoder ! smuxer.sink_0 nvstreammux name=smuxer  width=1920 height=1080 batch-size=1 batched-push-timeout=4000000 ! nvinfer config-file-path=dstest1_pgie_path.txt ! nvvideoconvert ! nvdsosd ! nvvideoconvert ! nvv4l2h264enc ! h264parse ! qtmux ! filesink location=test.mp4

The above command is right deepstream-test1 Command line simulation , But there is a lack of osd Probe function , So it's not complete , But it can also run , Mainly used to show nvstreammux request pad（sink_%u） Usage of . among nvv4l2decoder yes nvidia Hard decoding element ,nvstreammux yes deepstream Queue element , In the use of nvinfer This queue element must be used to add before reasoning nvinfer Data needed .nvinfer It's a reasoning element , The configuration file is dstest1_pgie_path.txt. of deepstream Information , Please check separately .

2. code

gst-launch-1.0 v4l2src device=/dev/video0 ! video/x-raw,format=YUY2,width=640,height=480,framerate=30/1 ! videoconvert ! x264enc ! h264parse ! qtmux ! filesink location=1.mp4 -e

Be careful , At the end of the -e Can't save , Press down ctrl-c Key will be sent to the video stream EOS identification , Video stream can be fully encoded .

3. rtp Push flow

The sender ：

gst-launch-1.0 v4l2src ! video/x-raw,format=YUY2,width=1280,height=720,framerate=10/1 ! videoconvert ! x264enc ! rtph264pay ! udpsink host=127.0.0.1 port=5600

The receiver ：

gst-launch-1.0 udpsrc port=5600 caps='application/x-rtp,media=(string)video,clock-rate=(int)90000,encoding-name=(string)H264' ! rtph264depay ! avdec_h264 ! videoconvert ! xvimagesink

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