Cypheros Transportstream Forum

Eng English-speaking Support => Specific problems with recordings of satellite/cable receivers => Thema gestartet von: DocKeeper am April 03, 2016, 17:26:28

Titel: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: DocKeeper am April 03, 2016, 17:26:28
Hi,
My source .ts files are HD 264 recordings of BBC4 via a sat tuner (an Octagon box running OpenPLI)
I use TS Doctor to extract the teletext subtitles into an SRT file, that works very well.

I wanted to use the TSDoctor Cut in and Cut out system, it has an excellent user interface and remove the start and end of the recording so that I only keep the real program.
However the resulting .ts (fixed) file always shows a disturbance at the cut in point. The version of TS Doctor is 2.0.21 and I-Frame only cutting has been selected. The cut in and cut out points are selected as I-Frames. The disturbance is so annoying that I cannot use the TS Doctor cutting system.

At the moment my only solution is to manually select the cut in and out points in Handbrake and make a MKV file with the fixed but uncut .ts stream and the .SRT file.

So how can TS-Doctor really select an I-Frame ? or is the BBC4 i_Frame not really an i-Frame ?
My understanding is that a cut-in at an i-Frame should be disturbance free, is that correct ? and if yes, are there any suggestions as to what I am doing wrong ?

thanks for any help !


To avoid this problem I note manually the cut in and out points and then mux the fixed  .TS file
Titel: Re: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: Mam am April 03, 2016, 20:29:00
yeah, its sad, but true  :o

TSDoc and BBC don't go together very well. It looks like the BBC Encoder is turned down to the max, obviously they carry over part of the pics even from AHEAD of the cut-in-Iframe so that very often (not always!) there is evil pixel-ation for a second or two.

My "solution" for this is a bit overdressed and I only use it, when the disturbences are really big and long. I cut in "one iframe before" already, use Handbrake to encode the whole video to 720p Mode and cut off the frames at the beginning which are too much now with a different tool efficiently cutting of the noise too.


Titel: Re: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: DocKeeper am April 03, 2016, 20:46:06
Many thanks for your prompt reply, I now know that I can better stick to Handbrake solution for the cut in and out points.
It is not very accurate, about 1 second.
But usually good enough for my purposes as the the start and end of the program is usually a rather a static second or two of video just showing credits.

You mention you use a different tool to cut the resulting Handbrake file, may I ask what one you recommend ?
Titel: Re: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: Mam am April 03, 2016, 20:51:56
You mention you use a different tool to cut the resulting Handbrake file, may I ask what one you recommend ?
Yeah I was afraid you would ask  ;D
Because I dont really have a good one currently, at least no cheap or free one.

If I really care about proper cutting I use Adobe Premiere (Elements). This adds another level of encoding, so I use it INSTEAD of Handbrake for these cases.

Luckily there are not really many films on BBC for me that are worth the efford (Adobe takes AGES! its nothing if you are in a hurry or have to do 10 films per day).

BTW, i never have problems on CUT-OUT! the disturbances are only on the first Cut-IN Point!

Titel: Re: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: Djfe am April 07, 2016, 22:11:55
So BBC is actually differing between IDR and I frames (unlike most other broadcasters)?

An explanation, what an IDR frame ist
H.264 introduced a second type of I frame that allows B frames to reference frames that are shown before I frames, but not if they were shown before an IDR frame
http://www.streaminglearningcenter.com/articles/everything-you-ever-wanted-to-know-about-idr-frames-but-were-afraid-to-ask.html (http://www.streaminglearningcenter.com/articles/everything-you-ever-wanted-to-know-about-idr-frames-but-were-afraid-to-ask.html)

One simple mistake in the article, I found
Zitat
if all I-frames are not IDR frames, you can see the distortion shown in the figure above if you drag back and forth in the file.
though I think he wanted to say:
Zitat
if not all I-frames are IDR frames, you can see the distortion shown in the figure above if you drag back and forth in the file.


Would it be possible for the TSD to detect and mark IDR Frames?
Titel: Re: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: ErichV am April 07, 2016, 23:47:57

Zitat
if all I-frames are not IDR frames, you can see the distortion shown in the figure above if you drag back and forth in the file.
though I think he wanted to say:
Zitat
if not all I-frames are IDR frames, you can see the distortion shown in the figure above if you drag back and forth in the file.

Both statements have the same meaning.  ;D
Titel: Re: Cut in disturbance with H264 HD video (BBC4)
Beitrag von: DocKeeper am April 12, 2016, 11:37:24
Many thanks Djfe for the excellent link, I learn something everyday!
As ErichV pointed out both your statements mean the same thing, all IDR frames are I frames, but not all I frames are IDR frames, if the person encoding has chosen it to be that way.
IDR frames are a subset of I frames.

But more importantly for TS Doctor, it would imply that using all types of I-Frames is not ideal. But the IDR frame would make a disturbance free cut-in and cut out point.
Wouldn't this be a good improvement for TS Doctor or is that a major change ?