Recording are always 1080i not 1080p

N

ntm1275

Member
I've been testing to see how well the HDR Fox T2 transfers HighDef recording to my PC, and the process is OK apart from being slow due to the 100mbit network card

The issue I have found is that a recording that is marked as being 1080p (1920 x 1080) when you press the 'i' button on the remote, appears to be downscaled to 1080i (1440 x 1080) after if is unencrypted

I used a program called MediaInfo on my PC to see the resolution of the video file

I initially though it was due to the fact that my TV can only handle 720p and 1080i, and so the Hummy was automatically downscaling the recording from 1080p to the lower setting (the Hummy at the time was set to 1080i), but if that was the case I would have expected that if I set the Hummy to 720p, then it would record to that setting (1280 x 720), but no it still downscales the recording to 1440 x 1080

Do you think that the 'i' button is displaying the wrong HighDef setting and it is not actually 1080p but 1080i, or is the Hummy definitely downscaling the recording when it is unencrypted

BTW I can't used MediaInfo or any other video utiliy to find out the settings for the unencryted recording as it just displays BDAV (No PAT/PMT): 8.61GiB, which I assume is because the recording is still encrypted, and so the utility cannot read it

After decrytion is displays:-

BDAV: 8.61 GiB, 2h 35mn
1 video stream: AVC
2 audio streams: AAC / AAC
1 text stream: DVB Subtile

First Video Stream
1440*1080 (16:9), at 25.000fps, AVC (High@L4.0) (CABAC / 4 Ref Frames

First Audio Stream
English, 48KHz, 2 channels, AAC (LATM) (LC)

Second Audio Stream
English, 48KHz / 24KHz, 1 channel, AAC (LATM) (HE-AAC / LC)

First Text Stream
English, DVB Subtitle

Has anybody got any idea on why it does this, or am I getting completely mixed up with what the settings/resolutions mean?
 
ntm1275 said:
I initially though it was due to the fact that my TV can only handle 720p and 1080i, and so the Hummy was automatically downscaling the recording from 1080p to the lower setting (the Hummy at the time was set to 1080i), but if that was the case I would have expected that if I set the Hummy to 720p,
Click to expand...
No that isn't how it works. The Humax simply records the stream as broadcast.
 
Thanks for clarifying that Martin

Then that brings me back to my two options:-

Do you think that the 'i' button is displaying the wrong HighDef setting and it is not actually 1080p but 1080i, or is the Hummy definitely downscaling the recording when it is unencrypted
Click to expand...
 
I don't think that any UK HD transmissions are in 1080p - BBC and ITV are 1080i, so it's almost certain that the 1080p message is incorrect.
 
All HD broadcasts in this country are 1080i, so the Hummy isn't downscaling.

Edit: Just saw the previous post, Sam Widges beat me to it!
 
ntm1275 said:
The issue I have found is that a recording that is marked as being 1080p (1920 x 1080) when you press the 'i' button on the remote, appears to be downscaled to 1080i (1440 x 1080) after if is unencrypted
Click to expand...

Someone will be able to verify this with more certanty than I but as far as I understand it:

1920x1080 and 1140x1080 can both be 1080p or 1080i. The 1080 refers to the vertical resolution which in both cases is 1080 lines/pixels. In the 1440x1080 broadcasts there is less horizontal resolution used, to save bandwidth I believe (I think the BBC use it).

I'm not sure what you are seeing, if it says 1080p then it looks wrong, if you are seeing 1920x1080 and assuming that means 1080p I think that assumption is wrong.

Progressive and interlaced are the two transmission mechanisms which are independent of the resolution, they simply describe whether all the lines are updated in one pass or only odd/even lines are updated each time.

As mentioned above no 1080p is broadcast in the uk because of the high bandwith required so you can get either:

720p (1080x720), 1080i (1920x1080) or 1080i (with less h-res) (1140x1080).

Ultimately, what is recorded is exactly what is broadcast as digital recorders just dump the stream to the hdd.

Hopefully i've got all my facts right above.
 
I can confirm that's right (work with design/manufacture of MPEG encoders), the 'i' (Interlace) or 'p' (Progressive) is independent of the resolution, although not any resolution can be 'i' or 'p'. Only 1080i is transmitted publicly as HD in UK, the only exception I've heard of anywhere is Fox Sports in US (obviously not relevant for us), who transmit 720p. If the Hummy is displaying 1080p, that doesn't correspond to the incoming transport stream.
 
Shaggy said:
I can confirm that's right (work with design/manufacture of MPEG encoders), the 'i' (Interlace) or 'p' (Progressive) is independent of the resolution, although not any resolution can be 'i' or 'p'. Only 1080i is transmitted publicly as HD in UK, the only exception I've heard of anywhere is Fox Sports in US (obviously not relevant for us), who transmit 720p. If the Hummy is displaying 1080p, that doesn't correspond to the incoming transport stream.
Click to expand...

Thanks, I had a vague recollection 1080i or 720p were picked depending on the content (sport being better at 720p) but I hadn't realised we used solely 1080i in the UK.
 
neilleeds said:
As mentioned above no 1080p is broadcast in the uk because of the high bandwith required ...:
.
Click to expand...

Not quite - since early last year, the BBC have been broadcasting 1080p on Freeview - see http://www.bbc.co.uk/blogs/researchanddevelopment/2011/04/software-upgrade-for-bbc-hd-on.shtml

Basically, the encoder can detect if the source is interlaced or progressive and encode accordingly, down to the GOP level. Therefore, it's perfectly feasible to see a mix of progressive and interlaced material within the same programme. I guess it depends on the box you are using to view it as to whether it shows it as 1080p or 1080i - my Panasonic TV always shows 1080i.

As for the resolution, normally both BBC One HD and BBC HD use 1440x1080. For the past few weeks BBC HD was at 1920x1080 for the recent 3D broadcasts, but it now seems to be back at 1440x1080.
 
renzz said:
Not quite - since early last year, the BBC have been broadcasting 1080p on Freeview - see http://www.bbc.co.uk/blogs/researchanddevelopment/2011/04/software-upgrade-for-bbc-hd-on.shtml

Basically, the encoder can detect if the source is interlaced or progressive and encode accordingly, down to the GOP level. Therefore, it's perfectly feasible to see a mix of progressive and interlaced material within the same programme. I guess it depends on the box you are using to view it as to whether it shows it as 1080p or 1080i - my Panasonic TV always shows 1080i.

As for the resolution, normally both BBC One HD and BBC HD use 1440x1080. For the past few weeks BBC HD was at 1920x1080 for the recent 3D broadcasts, but it now seems to be back at 1440x1080.
Click to expand...

Quite interesting how they can switch depending on the content, pans, credits etc.
 
Below is what I get when I press the 'i' button on the remote, but both show a resolution of 1440 x 1080 when decrypted

1080i
1080i.jpg


1080p
1080p.jpg
 
Hi

Regardless of 1080p or i, resolution doesn't change and is currently only 1440 x 1080.

The Humax information plate will tell you the encoder decided to encode as 1080p/25 or 1080/50i, it will swap almost in real time, so often at an edit it will change (recordings are the same). Only BBC HD currently has an encoder that switches dynamically.

Don't confuse this with anything new or suddenly getting better pictures. Before the BBC HD started doing this we would have only seen 1080/50i from the decoder, but anything that was progressive still gets to us and is seen by us on our TVs as a progressive picture, this is because 25p over 50i has been going on for decades in broadcasting and all modern HD TVs recognise 25p in 50i and reconstruct the original 25p.

Your TV will not signal anything if the Humax reports a change itself, as the signal over the HDMI cable doesn't alter. If you are outputting 1080/50i (my preferred output as that bypasses the de-interlacer in the Humax as most TVs do a better job), it goes something like this.

1080/50i -> encoder at the BBC sees 25p in the 50i -> encoded as 1080p/25 -> Humax decodes it as 1080p/25 -> HDMI output puts the 25p back into 1080/50i -> TV sees 25p in 50i and treats it as 25p, end result the same. Because 25p into 50i and vice versa is lossless, you get the same result.

As far as the BBC is concerned everything through their chain is 50i still. All that happens now is the encoder does the same as our HD TVs, it recognises 25p in 50i, and then encodes it as progressive rather than as interlaced footage. They do this because it is a bit more efficient to encode progressive footage as progressive, rather than treat it as interlaced when it isn't.

Because of improved efficiency, which is hardly that much, it gives the BBC the standard excuse to use along the lines of, "As we have improved our encoders we've been able to reduce the bit-rates without effecting the image quality".

So along with lower than they should be bit-rates, as you have found we also only get 1440 x 1080, which some call HD Lite.

Regards

Phil
 
Looks like one of the options from my first post applies to all this then
or am I getting completely mixed up with what the settings/resolutions mean?
Click to expand...

But at leased it now clarifies things for everybody
 
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