Why it matters. RTP and its companion control protocol (RTSP) are still widely used, and gaining traction
with the advent of HTML5-focused WebRTC (Real-Time
Communications) audio and video conferencing. RTSP
doesn’t actually transmit the streaming data, but does
align the content in a time-sensitive manner. Since
RTP and RTSP are based around UDP, they view time
sensitivity as more important than TCP’s approach of
“playing nicely” with other non-time-sensitive data on
Transmission Control Protocol (TCP)
Percentage vote: 71%
Definition. Transmission Control Protocol (TCP) is a
standards-based protocol designed for transmitting text
and ASCII data across the internet and other IP-based
networks. It provides automatic detection and retransmission of lost packets, resulting in accurate end-to-end
transmission but also often resulting in considerable
Why it matters. TCP is primarily designed to deliver non-time-sensitive content, and is a bit “chatty” in
that it confirms receipt of content sent from server to
client. This means it is more reliable, but less timely,
than UDP. Streaming delivery via TCP is a relatively new development, mainly due to the use of HTTP-based, small-file delivery solutions like MPEG-DASH
or Apple’s HTTP Live Streaming (HLS) technology.
User Datagram Protocol (UDP)
Percentage vote: 57%
Definition. User Datagram Protocol is a method of communicating between computers that does not guarantee
that every bit arrives at its end destination. It’s favored
for time-sensitive data such as streaming media, including RTSP delivery. Using UDP to deliver time-sensitive
video content has led to a number of derivatives, often
called Reliable UDP (R-UDP), that attempt to mimic
some part of TCP’s confirmation of delivery.
Why it matters. UDP delivery is often opposed by net-
MPEG- 4 System (MPEG- 4)
work administrators, who prefer the “plays fair” ap-
proach of TCP data. In use cases such as videoconfer-
encing or video telephony, though, where shorter delay
(lower latency) delivery times are key, it is not practi-
cal to confirm that every data packet has arrived. Yet
enough data has to arrive so the video is subjectively
viewable and the corresponding audio plays smoothly.
Several approaches, such as R-UDP and Forward Error
Correction (FEC), have been attempted to address the
loss of some video data. These additions to UDP hold
great promise, but each causes additional latency in
the initial encoding.
Percentage vote: 57%
Definition. A system containing audio and video codecs
(AAC, H.264), container formats (MP4), metadata, and
system protocols for MPEG- 4 audio and video storage
and delivery. Based on the initial Quick Time interactive authoring system and its Sprites concept.
Why it matters. MPEG- 4 System is the overarching solution for interactivity that the MPEG standards committee put forward as an alternative to Macromedia Flash
(later Adobe Flash). It defined a number of key elements,
including timed-text and closed-captioning titles as
well as innovations such as motion paths (and accompanying blurs or motion elements) for alpha-channeled
still elements. MPEG- 4 started with a fairly limited video codec, which was replaced by MPEG- 4 Part 10 (aka
AVC or H.264).
MPEG- 4 ISO Base Media File Format
(MP4 aka MPEG- 4 Part 12)
Percentage vote: 57%
Definition. MPEG- 4 Part 12: Also known as the ISO
Base Media File Format, the standards-based MPEG- 4
Part 12 (ISO/IEC 14496-12) container format is identical to the text published for ISO/IEC 15444-12 (a part
of the JPEG 2000 still image standard). The MP4 extension, which is based on the QuickTime container format, is used for some (not all) ISOBMFF files.
For instance, Adobe Systems introduced the F4V
file format for Flash Video, noting it was based on
the ISOBMFF. Yet the F4V file format was not registered by the MP4 registration authority, although
the F4V technical specification is publicly available.
ISOBMFF may contain H.264 video compression and
MP3 or AAC audio compression. Microsoft announced
in 2009 a file format based on ISOBMFF with the extension ISMV, better known as Smooth Streaming and
the subsequent Protected Interoperable File Format
(PIFF). However, no mention was made of the WMA
compression format in ISOBMFF, so it may be unsupported by some platforms.
Why it matters. The MPEG- 4 system contained the
base media file format (MP4) long before it became
its own substandard, and MP4 survived as a container format even when the MPEG- 4 system faltered. Elementary streams for everything from mobile video
capture to desktop video editing tools to fragmented/