Capturing TV broadcast 4:3 and 16:9 DAR

[wiseant]

Hi

I wanted to capture a TV broadcast so I could view it later. Looks like I have two choices

I am in Canada using Telus Optik TV

1. Set TV Tuner to use a Screen aspect ratio of 4:3 standard definition
2. Set TV Tuner to use a Screen aspect ratio of Widescreen standard definition


So I did two tests using VirtualDub to capture 704x480 PicVideo mjpeg from an HD broadcast

1. 4x3.avi
https://forum.videohelp.com/attachment.php?attachmentid=39630&stc=1&d=1479774722

2. 16x9.avi
https://forum.videohelp.com/attachment.php?attachmentid=39631&stc=1&d=1479774722

1. I open the 4x3.avi in VirtualDub and set the aspect ratio to 4:3 and I get a video of 640x360 with black borders top and bottom

2. I open the 16x9.avi in VirtualDub and set the aspect ratio to 16:9 and I get a video of 852x480

Couple of questions
What would the broadcast resolution be?
What does the TV tuner do to get the 704x480 video?; one has a DAR of 4:3 and the other a DAR of 16:9

I would presume that the 16:9 capture is "better quality" or is it simply a case when I captured using "Widescreen standard definition" that the video was simply resized from the 4:3 Standard definition? How does interlacing work with a video that with the correct DAR is 640x360?


TIA

[LMotlow]

Resampled while interlaced. The aliasing and line twitter are so annoying I can't stand watching these.

[manono]

1. I open the 4x3.avi in VirtualDub and set the aspect ratio to 4:3 and I get a video of 640x360 with black borders top and bottom

You should get 640x480 with black on top and bottom.

I would presume that the 16:9 capture is "better quality"...

Yes, much.

I know nothing about Canadian broadcast resolutions. You can't capture a hi-def stream? As LMotlow mentions, the aliasing is pretty bad.

Resampled while interlaced. The aliasing and line twitter are so annoying I can't stand watching these.

If you're saying it was resized improperly, I see no signs of that. Bob it and I think you'll agree.

[wiseant]

@LMotlow

Resampled while interlaced. The aliasing and line twitter are so annoying I can't stand watching these.

Yes, I noticed these. So, they are broadcasting in 1080i, then the Tuner is resizing to 360px height?



@manono

You should get 640x480 with black on top and bottom.

Yes - what I meant was the actual image size is 640x360 [i.e 16:9] with 60px black top and bottom

You can't capture a hi-def stream?

No I just have a SD capture card using SVideo input

If you're saying it was resized improperly, I see no signs of that. Bob it and I think you'll agree.

Good idea, I am going to Bob it and see...


I did a lot of capturing as well as DVDRecording of hockey and football games in the past, and was pleased with the results before the switch was made to 16:9 digital. I decided to hook up my capture card the other day and needless to say I am not impressed.

Many stations have an HD and a SD channel - when I view the same content on their SD station it looks the same - so the TV Tuner is not resizing this - what resolution are they broadcasting for their SD channel? I need to do a capture from their SD channel to make sure.

So it looks like anyone watching a TV show on their SD TV is getting a substandard viewing experience regardless of whether they are watching an HD or a SD broadcast

And, if I want to make a proper capture I have to capture from a SD station that still broadcasts 480px height?


TIA

[usually_quiet]

Good idea, I am going to Bob it and see...


I did a lot of capturing as well as DVDRecording of hockey and football games in the past, and was pleased with the results before the switch was made to 16:9 digital. I decided to hook up my capture card the other day and needless to say I am not impressed.

Many stations have an HD and a SD channel - when I view the same content on their SD station it looks the same - so the TV Tuner is not resizing this - what resolution are they broadcasting for their SD channel? I need to do a capture from their SD channel to make sure.

So it looks like anyone watching a TV show on their SD TV is getting a substandard viewing experience regardless of whether they are watching an HD or a SD broadcast

And, if I want to make a proper capture I have to capture from a SD station that still broadcasts 480px height?


TIA

The vertical resolution for SD channels has to be 480, as you surmised, but there is no way to tell the horizontal resolution used for broadcast if you are using an analog capture device.

If SD QAM channels from your cable company conform to the ATSC spec, the video might be broadcast at any of several resolutions. I have a PC TV tuner device for over-the-air TV and a PC CableCARD tuner for cable TV, and have seen the following used for SD content: 720x480, 704x480, 640x480, 528x480

You are correct to think that these days the SD version of an HD channel is often created by downscaling an HD source at the cable company's headend, possibly applying letterboxing in the process.

My last cable box would only letterbox all HD channels for output using its RF, composite, and S-Video connections. You are lucky to have a cable box that can provide anamorphic widescreen from its S-Video connection (your 16:9 sample) for HD channels. That is indeed what you should use for recording, if possible. (You would need to capture at 854x480 for square pixels).

[LMotlow]

[QUOTE=manono;2467456]

Resampled while interlaced. The aliasing and line twitter are so annoying I can't stand watching these.

If you're saying it was resized improperly, I see no signs of that. Bob it and I think you'll agree.

I did bob it. It was still too aliased and twittery to watch.

[wiseant]

@usually_quiet

There doesn't seem to be any defacto standard for broadcasting SD content

I did some more tests. This is what I found

1. SD channel - TV Tuner Screen aspect ratio of 4:3 standard definition
Got the same result as from the same HD channel, i.e. 640x480 4:3 DAR 60px black top and bottom - aliased

2. SD channel - Screen aspect ratio of Widescreen standard definition
This simply added black to the left and right sides along with the 60px black top and bottom - aliased

3. SD channel APTN (Aboriginal People's Television Network)
TV Tuner Screen aspect ratio of 4:3 standard definition
This produced a proper "full-frame" 640x480 4:3 no black borders - OK - no aliasing

4. SD channel Knowledge Network
TV Tuner Screen aspect ratio of 4:3 standard definition
This was a weird one - the 640x480 4:3 DAR - pretty sure the actual image height was 410px and 35px black top and bottom = 640x480 - did not capture this one

5. SD channel PBS
TV Tuner Screen aspect ratio of 4:3 standard definition
This produced a proper "full-frame" 640x480 4:3 no black borders - no aliasing

6. SD channel PBS
TV Tuner Screen aspect ratio of Widescreen standard definition
This surprisingly produced a proper 16:9 DAR with no black borders - no aliasing

see: https://forum.videohelp.com/attachment.php?attachmentid=39649&stc=1&d=1479877716

It is just a talking head

[usually_quiet]

@usually_quiet

There doesn't seem to be any defacto standard for broadcasting SD content

I did some more tests. This is what I found

1. SD channel - TV Tuner Screen aspect ratio of 4:3 standard definition
Got the same result as from the same HD channel, i.e. 640x480 4:3 DAR 60px black top and bottom - aliased

2. SD channel - Screen aspect ratio of Widescreen standard definition
This simply added black to the left and right sides along with the 60px black top and bottom - aliased

3. SD channel APTN (Aboriginal People's Television Network)
TV Tuner Screen aspect ratio of 4:3 standard definition
This produced a proper "full-frame" 640x480 4:3 no black borders - OK - no aliasing

4. SD channel Knowledge Network
TV Tuner Screen aspect ratio of 4:3 standard definition
This was a weird one - the 640x480 4:3 DAR - pretty sure the actual image height was 410px and 35px black top and bottom = 640x480 - did not capture this one

5. SD channel PBS
TV Tuner Screen aspect ratio of 4:3 standard definition
This produced a proper "full-frame" 640x480 4:3 no black borders - no aliasing

6. SD channel PBS
TV Tuner Screen aspect ratio of Widescreen standard definition
This surprisingly produced a proper 16:9 DAR with no black borders - no aliasing

see: https://forum.videohelp.com/attachment.php?attachmentid=39649&stc=1&d=1479877716

It is just a talking head

There definitely are standards governing what resolutions and aspect ratios are allowed for TV broadcasts. Because these standards exist, letterbox bars and/or pillarbox bars must be added to fill the frame when the actual picture area does not. Cable boxes might also add letterbox bars when downscaling HD video for display on a 4:3 TV using SD video connections.

It is likely that you won't able to do anything about the captures with picture problems because the problems exist in the broadcast itself. Somebody didn't handle the video correctly somewhere along the way.

I recorded a few short clips from some SD cable channels last night using my CableCARD tuner. A CableCARD tuner allows capturing the MPEG-2 or H.264 broadcast stream as is. (CableCARDs aren't available in Canada, but they are available to consumers in the US due to an FCC decision made some years ago that required it.) I chose to record advertisements to be safe, in case I wanted to post some. I did find one sample with obvious problems.

[Edit]I added the same video bob deinterlaced with Handbrake, but when the computer screen scrolls the lines still vibrate.

[Pinto007]

I open the 4x3.avi in VirtualDub and set the aspect ratio to 4:3 and I get a video of 640x360 with black borders top and bottom

Man, it is letterboxed 704x480 video, not 640x360. SD has ALWAYS the same resolution 704x480, no matter if 16:9 or 4:3. SD 16x9 is not resized, is stretched horizontally.