[vlc] Re: optimum bitrate for streaming Mpeg2-ts

[Jean-Paul Saman]

Peter Maersk-Moller wrote:

> Hi Jean-Paul
>
> Jean-Paul Saman wrote:
>
>> Jeroen Heijhoff wrote:
>>
>>> Hello,
>>> I'd like to know if there is a optimum bitrate for streaming 
>>> MPEG2-ts streams.
>>> I want to go streams MPEG2-ps to MPEG2-ts and I just want to know if 
>>> streaming
>>> 5Mbps streams instead of (for instance) 4Mbps really does add 
>>> something to quality etc.
>>
>> To make matters even more confusing:
>> A general bitrate of about 3.5MBps / 4MBps (like in DVB streams) can 
>> easily go upto 8 MBps temporarily when using VBR (Variable Bitrate 
>> encoding). Which is general more used then CBR (Constant Bitrate 
>> encoding).
>
>
> Hmm, how does it work on a transponder with a fixed bandwidth ?
>
> I assume that a generic satellite transponder has a fixed bandwidth
> of approx 45Mbps ? Since the transponder usually (not always) has
> mutiple TV-channels and audio channels, they can not all peak
> at 8-9 Mbps at the same time. Is there some reserved common
> pool of spare bandwidth that they can share and use if available.
>
In the rare occasion that this happens one of the streams is going to 
suffer. Or all are going to suffer slightly. I can imagine that if the 
satellite encoder/packetiser can predict it it will either delay some 
packets a bit or just do not encode/packetize all details for a scene. I 
do not know how these algorithmes work.

> If yes, then I assume they sometimes can not use the extra bandwidth
> leading to a temporary corruption in a stream ?
>
That could happen indeed. It will show up as lost packets I guess.

-- 

Many greetings,
     Jean-Paul Saman

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