Gst-nvstreammux New Alpha

The Gst-nvstreammux plugin forms a batch of frames from multiple input sources. When connecting a source to nvstreammux (the muxer), a new pad must be requested from the muxer using gst_element_get_request_pad() and the pad template sink_%u. For more information, see link_element_to_streammux_sink_pad() in the DeepStream app source code. The muxer forms a batched buffer of batch-size frames. (batch-size is specified using the gst object property.) The muxer forwards the frames from that source as a part of the muxer’s output batched buffer. The frames are returned to the source when muxer gets back its output buffer. The muxer pushes the batch downstream when the batch is filled or the batch formation timeout calculated from the overall and stream specific “fps” control configuration keys in provided streammux config file is reached. The timeout starts running when the first buffer for a new batch is collected. The default overall max and min fps for batch generation are 120 and 5 respectively. The muxer’s default batching uses a round-robin algorithm to collect frames from the sources. It tries to collect an average of ( batch-size/num-source ) frames per batch from each source (if all sources are live and their frame rates are all the same). The number varies for each source, though, depending on the sources’ frame rates. The muxer attaches an NvDsBatchMeta metadata structure to the output batched buffer. This meta contains information about the frames copied into the batch (e.g. source ID of the frame, original resolutions of the input frames, original buffer PTS of the input frames). The source connected to the Sink_N pad will have pad_index N in NvDsBatchMeta. The muxer supports addition and deletion of sources at run time. When the muxer receives a buffer from a new source, it sends a GST_NVEVENT_PAD_ADDED event. When a muxer sink pad is removed, the muxer sends a GST_NVEVENT_PAD_DELETED event. Both events contain the source ID of the source being added or removed (see sources/includes/gst-nvevent.h). Downstream elements can reconfigure when they receive these events. Additionally, the muxer also sends a GST_NVEVENT_STREAM_EOS to indicate EOS from the source. The muxer supports calculation of NTP timestamps for source frames. It supports two modes. In the system timestamp mode, the muxer attaches the current system time as NTP timestamp. In the RTCP timestamp mode, the muxer uses RTCP Sender Report to calculate NTP timestamp of the frame when the frame was generated at source. The NTP timestamp is set in ntp_timestamp field of NvDsFrameMeta. The mode can be toggled by setting the attach-sys-ts property. For more details, refer to :doc: DS_NTP_Timestamp section NTP Timestamp in DeepStream.

Note

New nvstreammux is being released as an alpha feature (limited support). Users will be able to use the new streammux by setting the environment variable export USE_NEW_NVSTREAMMUX=yes. The existing nvsteammux shall be employed by default.

Inputs and Outputs

• Inputs

  • NV12/RGBA buffers from an arbitrary number of sources

  • mono S16LE audio buffers from an arbitrary number of sources

• Control Parameters

  • batch-size

  • config-file-path [config-keys detailed below]

  • num-surfaces-per-frame

  • attach-sys-ts

• Output

  • NV12/RGBA batched video buffer NvBufSurface or batch audio buffer NvBufAudio

  • GstNvBatchMeta (meta containing information about individual frames in the batched buffer)

Features

The following table summarizes the features of the plugin.

Gst-nvstreammux plugin features

Feature	Description	Release
New streammux with numerous config-keys supported in a separate mux config-file.	Introducing new streammux	DS 5.0

Gst Properties

The following table describes the Gst-nvstreammux plugin’s Gst properties.

Gst-nvstreammux gst-properties

Property	Meaning	Type and Range	Example Notes
batch-size	Maximum number of frames in a batch.	Integer, 0 to 4,294,967,295	batch-size=30
num-surfaces-per-frame	If non-zero, muxer scales input frames to this width.	Integer, 0 to 4,294,967,295	num-surfaces-per-frame=1 (Default)
config-file-path	Absolute or relative (to DS config-file location) path of configuration file for the Gst-nvstreammux element	String	config-file-path=config_mux_source30.txt

Differences between default and new streammux with respect to the GStreamer plugin properties are discussed in the table below:

Gst-nvstreammux differences from default nvstreammux

Default nvstreammux Properties	New nvstreammux Properties
batch-size	batch-size
num-surfaces-per-frame	num-surfaces-per-frame
batched-push-timeout	N/A; Streammux config file could be used to regulate output framerate.
width	N/A; Scaling and color conversion support Deprecated.
height	N/A; Scaling and color conversion support Deprecated.
enable-padding	N/A; Scaling and color conversion support Deprecated.
gpu-id	N/A; Accelerated Scaling and color conversion support Deprecated.
live-source	Deprecated
nvbuf-memory-type	N/A
buffer-pool-size	N/A
attach-sys-ts	attach-sys-ts
N/A	config-file-path

Mux Config Properties

Details on Streammux config-file groups and keys are summarized the following table.

Gst-nvstreammux config-file properties

Group	config-key	Description
[property]	algorithm-type	Defines the batching algorithm; uint 1 : Round-robbin if all sources have same priority key setting. Otherwise higher priority streams will be batched until no more buffers from them. Default: 1
	batch-size	The desired batch size; uint. This value will override plugin property and DS config file key “batch-size” for nvstreammux Default: 1 (or == number of sources if adaptive-batching=1)
	overall-max-fps-n	Numerator of the desired overall muxer output max frame rate fps_n/fps_d; uint Default:120/1
	overall-max-fps-d	Denominator of the desired overall muxer output max frame rate fps_n/fps_d; uint
	overall-min-fps-n	Numerator of the desired overall muxer output min frame rate fps_n/fps_d; uint Default: 5/1
	overall-min-fps-d	Denominator of the desired overall muxer output max frame rate fps_n/fps_d; uint
	max-same-source-frames	Max number of any stream’s frames allowed to be muxed per output batch buffer; uint The minimum of this value and key (max-num-frames-per-batch) will be used. Default: 1
	adaptive-batching	Enable (1) or disable (0) adaptive batching; uint Default: 1 If enabled, batch-size is == number of sources X num-surfaces-per-frame.
[source-config-N]	max-fps-n	Numerator of this source’s max frame rate fps_n/fps_d; uint Default: 60/1
	max-fps-d	Denominator of this source’s max frame rate fps_n/fps_d; uint
	min-fps-n	Numerator of this source’s min frame rate fps_n/fps_d; uint
	min-fps-d	Denominator of this source’s min frame rate fps_n/fps_d; uint
	priority	The priority of this stream; uint Default: 0 (highest priority) A higher value is a lower priority.
	max-num-frames-per-batch	Max number of this stream’s frames allowed to be muxed per output batch buffer; uint The minimum of this value and key (max-same-source-frames) will be used.