Using Ascp4 for streaming video

Ascp4 can be used for streaming and for regular file transfers. The syntax is similar to a regular ascp4 file transfer, but the source and destination are URI paths.

Required configuration for multicast-to-multicast transfers

The transfer user who authenticates the multicast-to-multicast video stream transfer must have no docroot that is configured in aspera.conf. A file restriction can be set instead to restrict access.

Run the following command to unset a docroot and set a file restriction:

> asconfigurator -x "set_user_data;user_name,username;absolute,AS_NULL;file_restriction,|restriction"

The restriction can be set to allow all access (*) or limited by protocol, hostname, or path:

Restriction Format Example
By protocol udp://*

tcp://*
By protocol and hostname udp://hostname*
By protocol, hostname, and port tcp://hostname:5000*

Basic Ascp4 usage for streaming

> ascp4 -l target_rate --mode=mode --host=remote_hostname --compression=none --user=username --read-threads=1 --write-threads=1 input_uri output_uri
  • The ascp4 -l target rate option must be sent to a value that is equal to or greater than the bit rate of the video.
  • Ascp4 streaming supports two transfer directions: send and recv.
  • The ascp4 command defaults to multiple threads, but for reliable and in-order transport of streams you must use only one read and write thread by specifying --read-threads=1 --write-threads=1.
  • The video stream source and destination can be udp://, tcp://, or file://. For more information, see Built-in I/O providers

For command line usage examples, see Ascp4 video streaming examples.

For more information about ascp4 options, see Ascp4 command reference.

Multicast URI syntax

The input multicast URI and the output multicast URI uses the same syntax.
multicast_protocol_scheme://stream_ip_address:port?option=value&option=value...

The multicast protocol scheme can be either udp or mcast. If the IP address of your video stream is a multicast address, ascp4 uses multicast regardless of the protocol scheme (in other words, both udp and mcast use multicast). To use unicast addresses, you must use the udp scheme.

You can configure properties of the stream by adding options to the URI after the question mark (?), each separated by an ampersand (&). The following table describes the supported options.

Option Description Default
pktbatch={1|0} How to handle packet read and write. If 1, batch read and write UDP datagrams. If 0, read and write one packet at a time. 1
batchmicros=N Timeout for batching, in microseconds. No default
maxsize=maximum_size Maximum stream length. No default
maxtime=maximum_time Maximum stream duration, in seconds. No default
maxidle=maximum_time Maximum idle duration, in seconds. No default
rcvbufsz=buffer_size Receive buffer size. 10 MB
sndbufsz=buffer_size Send buffer size. 10 MB
ifaddr=ip_address Multicast interface IP address. 0.0.0.0
srcaddr=ip_address Multicast source IP address. 0.0.0.0
ttl=hops Multicast time to live. 1
loopback=boolean Multicast loopback. 1