[mobily]

Hey all,

I have posted about this before but have just changed my TV and noticed that the Freeview HD tuner in the TV gives a crisper image than the V+ HD equivalent.

For example, I was watching the preview on BBC One HD with a clip from 'not going out' being shown. I noticed quite a bit of picture noise whilst watching via my V+ HD box and switched to the same channel via the aerial feed.

The difference in quality was noticeable, mainly less picture noise. I checked the picture settings and they were exactly the same.

What does everyone else think? If you could post whether you are using Tivo or V+ we might be able to establish if this is box specific or Virgin specific.

Thanks

[mobily]

Having done a bit of reading on this subject... (yes I am a bit geeky!) it would seem that the difference is down to Virgin transmitting in MPEG-2 format and Freeview HD in MPEG-4 format.

[Kal_El]

I've definitely found Freeview HD better quality than my old Virgin service. The picture break up was appalling on Virgin, which would also emit a high pitched squeal when it broke up. Really unsettling. We had their engineers out numerous times, they'd fix it for about twenty minutes then when they'd gone it would be back to its old ways.

[mobily]

Interesting.

It would seem that Sky broadcast in MPEG-4 on their HD channels (I may be wrong) which also give a far superior picture to the Virgin alternative.

[Ernie_C]

Originally Posted by mobily

Having done a bit of reading on this subject... (yes I am a bit geeky!) it would seem that the difference is down to Virgin transmitting in MPEG-2 format and Freeview HD in MPEG-4 format.

Please explain. I don't understand what difference the compression algorithm could make to the quality of the picture.

[halsteadk]

Originally Posted by Ernie_C

Please explain. I don't understand what difference the compression algorithm could make to the quality of the picture.

Conversely, I don't understand why you think it COULDN'T make a difference - they are different, lossy algorithms, the end result is bound to be different.

But any discussion of quality is irrelevant without considering the bitrate. Assuming MPEG-4 is roughly the same quality at half the bitrate of MPEG-2, and *if* both services use the same bitrate, then MPEG-4 will be higher quality.

Anyone able to confirm bitrates used by Virgin and Freeview?

[Ernie_C]

Originally Posted by halsteadk

Conversely, I don't understand why you think it COULDN'T make a difference - they are different, lossy algorithms, the end result is bound to be different.

But any discussion of quality is irrelevant without considering the bitrate. Assuming MPEG-4 is roughly the same quality at half the bitrate of MPEG-2, and *if* both services use the same bitrate, then MPEG-4 will be higher quality.

Anyone able to confirm bitrates used by Virgin and Freeview?

You are right that bitrate is the important factor.

Compression algorithm makes no difference to eventual quality, assuming the same starting bitrate.

In fact, you could probably make a case for saying that MPEG4 has more opportunity to reduce the quality.

MPEG4 takes more bits out in its compression, so has to put more back in.