[MPlayer-users] dcs-5300G video.vam howto play it
mencoder at lesshaste.plus.com
Mon Apr 10 23:49:40 CEST 2006
Reimar Döffinger wrote:
>> the dcs-5300G is a dlink camera.
>> The specs say
>> "H.263+ (MPEG4 short header mode)"
> Whatever you downloaded it is not H.263+, the picture header is invalid
> according to all (draft) specifications I could find.
> Now, I can't say anything about "MPEG4 short header mode", since MPEG-4
> specifications (even as drafts) are really hard to come by...
A quick web search shows some information about MPEG 4 short header mode.
See from http://www.m4if.org/resources/mpeg4userfaq.php
# *Does MPEG-4 Video support H.263?*
Yes. H.263 Baseline (No Annexes) is incorporated as part of MPEG-4. It
is known as 'short header' inside the specification.
There are different kinds of MPEG-4 compression. The most popular are
MPEG-4 ASP (Advanced Simple Protocol), MPEG-4 SP (Simple Protocol), or
MPEG-4 Short Header. MPEG-4 ASP generates frames of I, P and B type,
which improves compression factor, whilst MPEG-4 SP and MPEG-4 Short
Header give only I and P frames. MPEG-4 ASP and MPEG-4 SP are
implemented on ASIC chips (Application Specific Integrated Circuit),
whereas MPEG-4 Short Header uses DSP circuit (Digital Signal Processor).
The answer is: with the same picture quality the band needed for
transmission is considerably lower, or - with the same band - the
quality of picture is higher.
*3.6.3 MPEG-4 short header and long header
*Some network video streaming systems specify support for “MPEG-4 short
header,” so it’s important to understand this term. In fact it’s nothing
more than an H.263 video stream encapsulated with MPEG-4 video stream
MPEG-4 short header does not take advantage of any of the additional
tools specified in the MPEG-4 standard. MPEG-4 short header is only
specified to allow backwards compatibility with the H.263 recommendation
for video conferencing over ISDN and LAN. For practical purposes, MPEG-4
short header is identical to H.263 encoding/decoding, which gives a
lower quality level than both MPEG-2 and MPEG-4 at a given bit-rate. The
image and video quality in “short header” is not close to that of true
MPEG-4, since it does not make use of techniques that allow it to filter
out picture information that is not visible to the human eye. Nor does
it use methods like DC and AC prediction, which can significantly
decrease bandwidth demands.
To clarify a network video streaming system specification, support for
MPEG-4 is sometimes denoted “MPEG-4 long header,” which in other words
is the mode where the MPEG-4 compression tools are being used.
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