[opendtv] Re: [Mp4-tech] Re: HDTV and SDTV Decoders for MPEG-2 andMPEG-4 AVC
- From: Kon Wilms <kon@xxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 16 Feb 2005 10:14:33 -0800
On Wed, 2005-02-16 at 12:54 -0500, John Shutt wrote:
> It is more a matter of how the STB is designed internally. If the STB
> wished to, it could one MPEG stream from the IP multicast that you wish to
> cache and send it directly to hard drive, and send a second MPEG stream to
> the MPEG decoder for viewing. The cached program is docoded by the MPEG
> decoder at a later time when it is viewed. This is, I believe, how PVRs
> that are built into DBS STBs operate. So in this case only one MPEG decoder
> chip is required, and no MPEG encoder function is required.
>
> If, however, the designer of the STB wishes to give the user an option of
> several quality levels as a tradeoff for storage time per Mb, then the MPEG
> bitstream would have to be re-encoded at a lower bitrate than the original
> multicast. i.e. an original 2 Mbps MPEG multicast is downconvered to a 1
> Mbps stream for recording on the hard drive, reducing the video quality but
> increasing the number of hours of storage time on the hard drive. I do not
> know if this bit rate reduction would require a complete decode-encode
> cycle, or if there are encoders that can reduce the bitrate without a
> complete decode to baseband video.
If you play the data that is written to disk instead of forking the
stream, you can insert a transcoder (which doesn't necessarily 'require'
a 'complete' decode (I'm sure someone will beg to differ)) prior to the
disk write and not need to change your player's code and interfaces.
Unless ofcourse you want to view the stream in high bitrate while the
version saved to disk is lower bitrate. Its also easier on buffer
management to just play the stream from disk - overrating is never a
problem.
Cheers
Kon
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
