[linux-dvb] How does bad reception influence quality of macroblocks?

lynx.abraxas at freenet.de lynx.abraxas at freenet.de
Thu Feb 15 22:49:06 CET 2007


On 08/02/07 20:05:21, timecop wrote:
> You will lose one or more TS packets (188bytes) if RS decoder (or some
> other step before that) cannot fully recover the packet. Those packets
> are usually marked with 'transport error indicator' flag, and mpeg
> decoder skips them, or perhaps blindly tries to decode data in them.
> Usually results in ugly crap across the screen in a particular section
> that was ruined, even if it was only a single TS packet that was
> affected.
> 
> -t

Thanks  for  Your  reply.  After  reading some docs about mpeg-TS I still have
difficulties to realize the effects of loosing TS packets to  the  macroblocks
(16x16 pixels) of the mpeg-2 video. Is there at least one full macroblock in a
TS packet?

To put my question in other words:
If my dvb-t device doesn't get the  full  stream  will  this  always  lead  to
missing  macroblocks  or  can  it  yield  less  obvious  loss of quality (like
unsharpness)?

Does the type of device influence the qualtity of the recieved stream? (Why do
devices differ in prices so much?)

Thanks
Lynx

>
> On 2/8/07, lynx.abraxas at freenet.de <lynx.abraxas at freenet.de> wrote:
> >Hallo!
> >
> >
> >I have this general question to DVB-T:
> >How  is  the  qualtity of macroblocks influenced if my reception of the
> >signal
> >isn't perfect?
> >
> >I know macroblocks will be lost totally if the reception is not sufficient
> >any
> >more.  But  what happens in between these cases? Can a single macroblock
> >loose
> >information (quality) in the reception or will it be dismissed totally if
> >the
> >data of a macroblock is not recieved completly?
> >What is the behavior of DVB-S/C or mpeg-streams in general?
> >
> >
> >Thanks for any answers
> >Lynx



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