Knowing when a TV programme has been upscaled... programmatically!?

Forums › Home Theatre (including HTPC and EPG Collector) › Knowing when a TV programme has been upscaled... programmatically!?

geekPete

34 posts

Geek
Inactive user

#73546 15-Dec-2010 14:09

**Note that I also posted this question in the DVB-T forum at http://www.geekzone.co.nz/forums.asp?forumid=83&topicid=73545 before I found this forum - which maybe more appropriate for the question. I couldn't delete or edit my post, so if an Admin wants to delete one, please do :)
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Is there any way to find out the original pre-transmission resolution size of each program (SD, Half-HD or Full-HD)... maybe within the EPG info?

This is so a programming script can know if a program has been "upscaled" before transmission.

Why? ...

I generally re-encode programs that I have recorded using my PC-based PVR media server, because some of my viewing devices, or players, cannot handle fullHD resolution, nor some of the high-end "encoding options" in the stream, e.g. CABAC, AAC-HE, etc.

If this "upscaling" info was in the Program information, then if my conversion program could know that a 576 line source had been upscaled to 1080 lines, I would program it to re-encode back down to 576, not the transmitted 1080 line height, so it can be better viewed at no loss of quality on less powerful devices. Less importantly, it would also take up less hard drive space and use less network bandwidth when played over my wi-fi.

I'm using EPG Collector to read the transmitted MHEG stream, but the resulting XML file only shows the following fields for each program:

programme start,stop,channel

title

desc

rating

There is no "HD" field.

I've noticed that some programs that have an HD source resolution have a "HD" logo burned into the top-right of the video, but it's not really practical - from a programming viewpoint - to start analysing video frames in that way.

Any ideas how to get the info easier?

graemeh

2078 posts

Uber Geek

#417631 15-Dec-2010 14:19

No idea but it must be possible to do at least part of this as my Tivo separates programs into HD and not despite them all being broadcast at 1080i (on the HD channels).

One trick I use to save space is to record the TV3+1 version which from memory is 576i.

geekPete

34 posts

Geek
Inactive user

#417643 15-Dec-2010 14:29

From some looking around at the forums, it seems like we may be looking for the following tag in an XML file:

<quality>HDTV</quality>

I also wonder if it's possible to extract the source's original aspect ratio too, without analysing the video frames for black bars. E.g. Is it a 4:3 or 16:9 source?"

geekPete

34 posts

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Inactive user

#417651 15-Dec-2010 14:47

I should probably mention that I'm in Wellington, NZ, and getting my signal from Mt Kaukau. :)

dolsen

1476 posts

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#417660 15-Dec-2010 14:50

geekPete:
If this "upscaling" info was in the Program information, then if my conversion program could know that a 576 line source had been upscaled to 1080 lines, I would program it to re-encode back down to 576, not the transmitted 1080 line height, so it can be better viewed at no loss of quality on less powerful devices.

The tivo has its own guide, so, it is possible that they include more info from a source of data other than what is broadcast.

As per the above, You would still get a degradation in quality when reducing it back down. Even though the source was 576, it was unscaled to 1080. There will be averaging / smoothing etc, so, the signal is no longer the 576 that it once was. When you downscale, there will be more averaging, smoothing etc resulting in less detail. If I had the option, I wouldn't re-encode it again, but, I can see why you might want to.

geekPete

34 posts

Geek
Inactive user

#417723 15-Dec-2010 15:57

dolsen: If I had the option, I wouldn't re-encode it again, but, I can see why you might want to.

Just as an illustration of the benefits of this, I've just recorded and then re-encoded a 5000MB "Project Runway".TS file. Since the original broadcast was 4:3 in a 16:9 HD transmission, and obviously upscaled from 576i, I cropped 248 pix off each side to remove the black bars. To make the aspect ratio better viewable in my 16:9 and 16:10 screens, I cropped 48 pix off the top and 144 pix off the bottom (for a 16:10 result). When this was reduced down to a 720wide encoded size, it produced a file of only 640MB - a file almost 8 times smaller!

When visually comparing the result with the HD cropped and scaled up, and both at full screen, I can't tell the difference.

And the result also plays back fine on a 700MHz PIII laptop! (70-80% CPU using VLC Player)

[FYI: Used Handbrake 0.94 to encode to h.264 using AppleTV x264 settings, and an RF of 19.5]