Picture Quality of SKY+ vs FREEVIEW vs DVD

jpe20

Hi folks,

I am just curious after setting up my new media PC on what the difference in picture quality is between sky/freeview and dvd are. Just that my FREEVIEW (on media PC) seems to be nowhere near as good in quality as SKY. Fast moving scenes (eg panning shots over detailed landscapes) seem to shudder/stutter a bit on my FREEVIEW which hardly ever happens on SKY and is rarely noticible on DVDs.

I think I know the following!!!

(1) DVDs I guess are encoded at around 8Mbits/sec. Rough estimate based on 6GB of DVD space being used to store a 100min movie. ie 6000MB/6000secs = 1MB per sec = 8Mbits per sec

(2) From googling I found "unreliable" data that FREEVIEW channels can be encoded at 1.5Mbits/sec to 9Mbits/sec depending on transmission configuration.

(3) SKY+ .... I have no idea.

Reason for this is if at the end of the day the FREEVIEW channels are encoded at lower quality than SKY and DVDs then this goes a long way to explaining the poorer picture on Freeview than sky. If this is proven to be the case then I will just finish fiddling with various settings on my media PC. If it is not the case then I need to find out about possibly using a better video codec (I am using the standard cyberlink MPEG2 codec that came on PowerDVD 6) such that I can play around with its settings (the codec I have seems to have no settings options such that I can switch deinterlacing on/off etc). Also my monitor refresh rate of 60Hz could be a further source of problems as obviously FREEVIEW is PAL based at 50Hz.

Anyhow the above may sound if I am picky but I have spent alot of money on my new PC rig so I would like to get it as near perfect as possible.

Thanks for listening

Jules

woo

not sure if this helps - but too my pc freeview adapter into the office for the world cup and people commented on how much better the picture was over sky that they were used to. i haven't suffered any of the symptoms you describe when using the freeview stick

jpe20

I was being dumb b4 ... just realised that sky+ records MPEG2 transmission directly to the HDD. Knowing the size of the HDD in my box and taking my largest recording one at 175mins using up 6% of a 120GB disk. I worked out that the recording was 7200MB in size at 10500secs long making 0.7MB/sec = 5.5Mbits/sec.

So SKY transmissions are around 5Mbits/sec. I dunno if other channels are lower or higher based how the signal is broadcast. I am just comparing BBC1 sky to BBC1 freeview.

Any tips on better MPEG2 codecs (one that I can change detailed settings on) such that I can improve my FREEVIEW picture on MCE2005 will be appreciated.

Jules

magic_pants

woo wrote:

not sure if this helps - but too my pc freeview adapter into the office for the world cup and people commented on how much better the picture was over sky that they were used to. i haven't suffered any of the symptoms you describe when using the freeview stick

One thing to remember is that ITV provide a notoriously poor picture quality over satellite and so you will certainly notice a better picture via Freeview. This is due to the number of transponders that ITV utilise on the satellites and, this, the reduced amount of bandwidth available to each broadcast stream. i.e. ITV cram multiple ITV regions onto each transponder and so have to reduce the bandwidth to get each signal down to the end user. So ITV will, undoubtably, look better on Freeview. BBC I am not so sure and would be surprised if there was a difference. It is not just appalling programming that ITV is famous for!

magic_pants

http://www.linowsat.de/0282/tv/all.html

...will give you all the various bitrates for the Astra 28.2 satellite channels.

jpe20

Just read that the MCE 2005 recording format although being propriety to Microsoft it records in dvr-ms format apparently. This though is simply some information required by MCE + the pure MPEG2 transmission data. So I have just recorded a quick 10min program on FREEVIEW looked for the recorded file and found it to be 387MB in size at 600s length = 0.6MB/sec = 5.2Mbits/sec.

So FREEVIEW is around 5Mbits/s
SKY also at 5Mbits/sec. Is it VBR or CBR on these???

So they both have comparable picture quality in terms of the broadcasted signal. Time to look at my software again!!!!!

They must use a better decoding codec in the SKY box than what I am using on my PC????

One thing I notice on my Freeview(PC) is that scrolling text (ie News24 strapline) looks terrible its jerky compared to the much much smoother SKY scrolling text. Is the choice of codec used the cause of this.

Does any1 use a better/great MPEG2 decoder codec???? I don't mind buying one only if it will offer much better results than the POWERDVD 6.0(basic) codec I am using now.

Jules

Thanks for the info so far. Based on what woo said seems to confirm what I just worked out. And magic .... always wondered why ITV never looked too good on SKY!!! Not that I am missing much!!!

jpe20

Nice find magic ..... confirmed my rough calculation of BBC1 (sky) being transmitted at 5Mbits/sec.

Jules

marks87

jpe20 wrote:

So FREEVIEW is around 5Mbits/s

Different channels have different bitrates. For example, BBC1 on Freeview runs at between 4Mbps and 6Mbps (depending on whether you live in Scotland, England or Wales. England is nearer 6, with Scotland and Wales down at 4, to allow for local radio stations and their data services). ITV channels, on the other hand, are lucky to get beyond 3Mbps.

There is also a technique called "stat-muxing". This means channels are given more bitrate depending on what they're showing. So if, for example, ITV4 is showing a football match (high motion), the bitrate of some of the other channels can be reduced to give ITV4 some more.

jpe20

I've just setup my XBOX 360 to access Windows MCE 2005. Watching channels on that is ideal ... no jerky scrolling text issues etc looks as good at least to Sky + when watching live/recorded TV.

PC then is obviously deficient .... are all software MPEG2 decoder codecs poor when compared to hardware codecs??? So I am going to investigate tomorrow whether I should/need to get around my 60Hz issue on my Dell 24 FP monitor or need a new codec or finally need to change some other windows settings. I assume my processor 3800x2 AM2 is good enough???

Jules