[waldo22]

I have a question about a "problem" that isn't really a problem.

I need an academic explanation for what's going on with some basic transport stream cutting.

I use an R5000-HD modification to record unmodified transport streams directly from my Dish Network service.

I just recently tried editing a few of these streams with a nifty program (no longer in development) called TSSniper.

It seems to good to be true...

It supposedly just "cuts" the transport streams at the specified locations, without any transcoding or other alterations.

That's why I am very surprised at how much smaller the output files seem to be than the original recordings.

For instance, my recording of the animated film "How to Train Your Dragon" was originally around 15 Gigs:

Code:

Mediainfo:
Complete name                    : How to Train Your Dragon (2010).ts
Format                           : MPEG-TS

ID                               : 17 (0x11)
Menu ID                          : 1 (0x1)
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : [email protected]
Format settings, CABAC           : Yes
Format settings, ReFrames        : 3 frames
Codec ID                         : 27
Duration                         : 1h 46mn
Bit rate                         : 18.0 Mbps
Width                            : 1 440 pixels
Height                           : 1 080 pixels
Display aspect ratio             : 16:9
Frame rate                       : 29.970 fps
Standard                         : Component
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Interlaced
Scan order                       : Top Field First
Bits/(Pixel*Frame)               : 0.387
Stream size                      : 13.4 GiB (93%)

I used TSSniper to cut about 1 minute off the beginning and 8 minutes off the end, and now I have a file that's under 3 Gigs!!!:

Code:

Mediainfo:
Complete name                    : How to Train Your Dragon (2010).ts
Format                           : MPEG-TS

ID                               : 17 (0x11)
Menu ID                          : 1 (0x1)
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : [email protected]
Format settings, CABAC           : Yes
Format settings, ReFrames        : 3 frames
Format settings, GOP             : M=4, N=32
Codec ID                         : 27
Duration                         : 1h 37mn
Bit rate                         : 3 644 Kbps
Width                            : 1 440 pixels
Height                           : 1 080 pixels
Display aspect ratio             : 16:9
Frame rate                       : 29.970 fps
Standard                         : Component
Color space                      : YUV
Chroma subsampling               : 4:2:0
Bit depth                        : 8 bits
Scan type                        : Interlaced
Scan order                       : Top Field First
Bits/(Pixel*Frame)               : 0.078
Stream size                      : 2.49 GiB (86%)

I have only included the video information, as the audio info is exactly the same.

I should note here that ALL of my Satellite TS recordings report a bit rate of exactly 18.0 Mbps for the video stream before I "cut" them, but display varying bit rates of between 3 and 5 Mbps after I cut them.

I can't tell any difference in the video quality with my untrained eye.

Can someone explain what's going on here?

Is the satellite provider "padding" the streams to make them exactly 18.0 Mbps to comply with some type of TS standard?

If I'm not losing any quality, I'm going to trim up all of my recordings - saving 12 GiB per film!

-Wes

[The Mariner]

Howdy,

I'll start off by saying I'm not an expert on this, but I think the reduction in file size is shown in the 'Bits/(Pixel*Frame)' value. The edited version of your movie has a significantly lower value & allowing for the difference in movie length, the % difference between the two filesizes is roughly proportional to the % difference in Bits/(Pixel*Frame).

If you cannot see any differences in quality then there is no reason why you shouldn't continue to use TSSniper to edit/reduce the filesize of your recordings. I have heard that in some cases the output files from TSSniper aren't 100% standards compliant, but if this doesn't cause you a problem then don't worry.

I use 'VideoReDo' to edit my DVB .ts recordings. It's frame-accurate & edited files can be re-saved in .ts format or transcoded into smaller filesize containers like .avi, mkv etc. It's not freeware though

[waldo22]

Howdy,

I'll start off by saying I'm not an expert on this, but I think the reduction in file size is shown in the 'Bits/(Pixel*Frame)' value. The edited version of your movie has a significantly lower value & allowing for the difference in movie length, the % difference between the two filesizes is roughly proportional to the % difference in Bits/(Pixel*Frame).

If you cannot see any differences in quality then there is no reason why you shouldn't continue to use TSSniper to edit/reduce the filesize of your recordings. I have heard that in some cases the output files from TSSniper aren't 100% standards compliant, but if this doesn't cause you a problem then don't worry.

I use 'VideoReDo' to edit my DVB .ts recordings. It's frame-accurate & edited files can be re-saved in .ts format or transcoded into smaller filesize containers like .avi, mkv etc. It's not freeware though

Thanks for the reply and the suggestion re: VideoReDo. I don't mind if it's not freeware if it works well. Frame-accurate would be nice.

I found an answer to the question over on the AVS Forum:
http://www.avsforum.com/avs-vb/showthrea...st21138840

(go to the last page if the link doesn't take you there)

Basically, the application I'm using to record fills the Transport Stream with "null packets" to make the bit rate constant.

Editing the TS gets rid of all the null packets.

Apparently older hardware wasn't able to handle Variable Bit Rate Transport Streams.

...so it looks like I just freed up a few TB of disk space

-Wes