<p>Containers like LXF/GXF/MXF allow EIA-708 (VBI) streams but as far as I know they do not encode the video data -- the blanking interval -- that originally contained those streams. That would run counter to the idea that codecs embody, that of squeezing out redundant information. I could be wrong, but I've never seen or heard of a codec that encodes invisible lines.</p>

<p>You could scan the file for the packet headers that identify caption / VBI streams, and if you find them you could impute a frame size that would have contained them, but you could do that anyway: any encoded video, if it were output as a TV signal, would have associated blanking, whether it contained captions or not.</p>

CC BY-SA 3.0
2015-08-09T14:01:08.517Z
These are SD files. I.e Eia 608.  You can read more here https://en.m.wikipedia.org/wiki/EIA-608
Johan Skaneby
CC BY-SA 3.0
2015-08-09T14:03:46.460Z
You can read about EIA 608 here https://en.m.wikipedia.org/wiki/EIA-608
Johan Skaneby
CC BY-SA 3.0
2015-08-09T14:04:38.620Z
So back to the original question - how to detect the presence of these lines?  which tool?
Johan Skaneby
CC BY-SA 3.0
2015-08-09T15:50:39.617Z
@JohanSkaneby Your question is about **lines** and **frame size** which are the wrong questions. These lines do not exist as video and do not affect the frame size. Only the data carried in those lines is stored in the container, alongside the video. Google "LXF VBI data" and you'll find pointers to tools that can find and read this data. It's a question of opening the file and scanning for headers.
Jim Mack
CC BY-SA 3.0
2015-08-09T16:03:58.830Z
What about line 21 and line 22?
Johan Skaneby
CC BY-SA 3.0
2015-08-09T16:08:21.663Z
Ok - anyway tnx for your time. We do not agree on basic technical background to my question. And Google for the answer is of course one of the ways to find the answer ;-)
Johan Skaneby
CC BY-SA 3.0
2015-08-09T17:36:03.670Z
@JohanSkaneby Lines 21 & 22 are not considered part of active video and are not usually digitized. If they contain data it can be extracted and encoded as a separate stream. I had no difficulty locating tools via Google to examine LXF VBI streams, so yes, Google is your friend.
Jim Mack
CC BY-SA 3.0
2015-08-09T13:56:35.580Z
2015-08-09T13:56:35.580Z
Jim Mack
<p>Is there a way to detect if a file has or has not Vbi data this way! 
I.e if a Pal videofile with the reported 720x576 has Vbi data the actual height is an additional 32 lines = 608.</p>

<p>SD pal file VBI = 720x608 </p>

<p>I am not interested in the info in those 32 lines - I just want to know if they are present or not ( to be able to make an decicion)</p>

<p>So far from what I can see ffmpeg and Medialinfo reports my VBI samples as 720X576 - but I know they are 608. </p>

<p>Maybe I am using the wrong tools or the wrong flags / cli arguments? </p>

<p>Many tnx!</p>

CC BY-SA 3.0
2015-08-08T17:20:38.560Z
It would be very unusual for the horizontal and vertical blanking to be included in an encoded digital file. Why do you believe that these files have that information?
Jim Mack
CC BY-SA 3.0
2015-08-08T17:45:45.243Z
Because fx Carbon detects the  file as 720x608 - and will output these lines unless I crop of 32 lines on the top. ( Carbon has an automatic detection / crop also - because other workflow Considerations I can't use that)
Johan Skaneby
CC BY-SA 3.0
2015-08-09T12:51:44.763Z
Sorry to be dense, but are you talking about a digital file on disk? If so, what type is it (container and codec)?
Jim Mack
CC BY-SA 3.0
2015-08-09T13:03:56.793Z
Yes - we are talking about a digital file, correct. So far LXF and Mxf. long gop Mpeg 2 inside
Johan Skaneby
<video><ffmpeg>
Detecting VBI or true video height?
Johan Skaneby
# Detecting VBI or true video height?

(Asked by: username_0 on 2015-08-08)

Is there a way to detect if a file has or has not Vbi data this way!
I.e if a Pal videofile with the reported 720x576 has Vbi data the actual height is an additional 32 lines = 608.

SD pal file VBI = 720x608

I am not interested in the info in those 32 lines - I just want to know if they are present or not ( to be able to make an decicion)

So far from what I can see ffmpeg and Medialinfo reports my VBI samples as 720X576 - but I know they are 608.

Maybe I am using the wrong tools or the wrong flags / cli arguments?

Many tnx!

**Tags:** video, ffmpeg

> **Comments:**
> **username_1**: It would be very unusual for the horizontal and vertical blanking to be included in an encoded digital file. Why do you believe that these files have that information?  
> **username_0**: Because fx Carbon detects the  file as 720x608 - and will output these lines unless I crop of 32 lines on the top. ( Carbon has an automatic detection / crop also - because other workflow Considerations I can't use that)  
> **username_1**: Sorry to be dense, but are you talking about a digital file on disk? If so, what type is it (container and codec)?  
> **username_0**: Yes - we are talking about a digital file, correct. So far LXF and Mxf. long gop Mpeg 2 inside  

---

## 1 answers

### Answer by username_1 on 2015-08-09. Score: 1

Containers like LXF/GXF/MXF allow EIA-708 (VBI) streams but as far as I know they do not encode the video data -- the blanking interval -- that originally contained those streams. That would run counter to the idea that codecs embody, that of squeezing out redundant information. I could be wrong, but I've never seen or heard of a codec that encodes invisible lines.

You could scan the file for the packet headers that identify caption / VBI streams, and if you find them you could impute a frame size that would have contained them, but you could do that anyway: any encoded video, if it were output as a TV signal, would have associated blanking, whether it contained captions or not.

> **Comments:**
> **username_0**: These are SD files. I.e Eia 608.  You can read more here https://en.m.wikipedia.org/wiki/EIA-608  
> **username_0**: You can read about EIA 608 here https://en.m.wikipedia.org/wiki/EIA-608  
> **username_0**: So back to the original question - how to detect the presence of these lines?  which tool?  
> **username_1**: @JohanSkaneby Your question is about **lines** and **frame size** which are the wrong questions. These lines do not exist as video and do not affect the frame size. Only the data carried in those lines is stored in the container, alongside the video. Google "LXF VBI data" and you'll find pointers to tools that can find and read this data. It's a question of opening the file and scanning for headers.  
> **username_0**: What about line 21 and line 22?  
> **username_0**: Ok - anyway tnx for your time. We do not agree on basic technical background to my question. And Google for the answer is of course one of the ways to find the answer ;-)  
> **username_1**: @JohanSkaneby Lines 21 & 22 are not considered part of active video and are not usually digitized. If they contain data it can be extracted and encoded as a separate stream. I had no difficulty locating tools via Google to examine LXF VBI streams, so yes, Google is your friend.  

---

