DASHing Towards Hollywood
21 June 2018
/ tcp-hollywood
Saba Ahsan presented our paper
DASHing Towards Hollywood at the ACM Multimedia Systems Conference
in Amsterdam, The Netherlands, last week.
This paper presents an implementation of the MPEG-DASH streaming video
standard running over TCP Hollywood, a variant of TCP we've developed
that's intended to be better suited for latency sensitive applications
than standard TCP.
The majority of streaming video content on the Internet is delivered on
HTTP connections running over TCP. The video content is segmented into
chunks of a few seconds duration, each encoded as several variants with
different bit rates. The client fetches chunks in sequence, based on a
manifest file that provides an index. The variant to download for each
chunk is chosen based on the client's estimate of the available network
capacity. The MPEG DASH standard defines a standard manifest format and
operational modes and procedures.
Such adaptive streaming over HTTP has become the de-facto standard for
video delivery over the Internet, partly due to its ease of deployment
in the current heavily ossified network. While it performs well in most
on-demand scenarios, it is bound by the semantics of TCP. These give
priority to reliability over timeliness, even for live video where the
reverse may be desired. This leads to high latency and start-up delays
for video streaming, since running with reduced play-out latency runs
the risk of stalls, waiting for TCP to retransmit lost segments.
TCP Hollywood is a variant of TCP we have designed. It provides a
framed multi-stream abstraction within a wire-compatible TCP flow,
and avoids head-of-line blocking by allowing frames to be delivered
out-of-order and to be discarded if they cannot be delivered in time
to meet a deadline.
Out-of-order delivery in TCP Hollywood allows a video player to measure,
adapt and request the next video chunk even when the current one is
only partially downloaded. Furthermore, the ability to skip frames,
enabled by multi-streaming and out-of-order delivery, adds resilience
against stalling for any delayed messages. In the paper, we show that
in high latency and high loss networks, TCP Hollywood significantly
lowers the possibility of stall events and also supports better quality
downloads in comparison to standard TCP, with minimal changes to
current adaptation algorithms.
Reproducibility
To aid with reproducibility, we provide all of the source code used in
generating the results described in the paper, with a Makefile
that describes and performs the process of performing the experiments,
processing and graphing the results, and producing the paper. This is
available from
The University
of Glasgow Research Data Repository or from
this website.
The mmsys2018hollywood.tar.gz file that can be retrieved from
the University of Glasgow is 12849004960 bytes in size
(SHA256: 5b2df6fa3db35fd842af9f40fa27faf8450eed3a951d5c915926fc3de8380fd6)
and is a complete archive.
The ahsan2018dashing.tar.gz file that can be retrieved from
this site is 2005076138 bytes in size
(SHA256: b7ac8aeb100bea0d789a11b24cca9be5be9d0c352ca8eca4ec25e6d8901c29c1).
The difference is that the file mmsys2018hollywood/stage3/big_buck_bunny_1080p.y4m.xz
has been removed from the copy of the archive hosted here.
This file can be retrieved from media.xiph.org
and is 10842485720 bytes in size
(SHA256: ccd84847324cc249b1822fc6b9e16544fc3e4470a515925cb0f48eca361cd1f8).
The contents of the two archives are otherwise identical.