Trimming a few seconds of SD from a HD MPEG-2

[silentg]

I have several MPEG-2 files that originated on a Series 3 Tivo. After transfer and decoding, I am looking to transcode and archive them. It seems however, that the station switched from a standard definition signal to a high definition signal about 10 seconds into each recording. Every program that I have tried to use to trim those first 10 seconds crashes when it gets to the resolution switch. Womble MPEG Wizard deals with the switch without crashing but when I try to export the trimmed video, it thinks the file is still standard definition. I tried using mencoder (mencoder -ss 00:00:10 -ovc copy -oac copy source.mpg -o result.mpg) but it crashes after a few percent with the error "too many audio packets in the buffer."


Has anyone ever seen multiple resolutions in a single MPEG file like this? Any ideas on how to trim that first 10 seconds of SD video out?

Thanks,
Scott

[Megahurts]

silentg,

I haven't seen multiple resolutions in a tivo file.

What does Mediainfo say about the resolution of the Tivo file (text mode)?

How are you decoding the Tivo transfers? I'm assuming you're using Video Redo. If so, have you tried cutting the first 10 sec before saving?

[silentg]

Here is the Mediainfo output for an example file:

General
Complete name                    : D:\temp\tivo\example.mpeg
Format                           : MPEG-PS
File size                        : 5.38 GiB
Duration                         : 59mn 59s
Overall bit rate                 : 12.9 Mbps

Video
ID                               : 224 (0xE0)
Format                           : MPEG Video
Format version                   : Version 2
Format profile                   : Main@Main
Format settings, Matrix          : Default
Duration                         : 59mn 59s
Bit rate mode                    : Constant
Nominal bit rate                 : 15.0 Mbps
Width                            : 720 pixels
Height                           : 480 pixels
Display aspect ratio             : 4/3
Frame rate                       : 29.970 fps
Standard                         : NTSC
Colorimetry                      : 4:2:0
Scan type                        : Interlaced
Scan order                       : Top Field First
Bits/(Pixel*Frame)               : 1.448

Audio #1
ID                               : 189 (0xBD)
Format                           : AC-3
Format/Info                      : Audio Coding 3
Duration                         : 59mn 59s
Video delay                      : -372ms

Audio #2
ID                               : 128 (0x80)
Format                           : AC-3
Format/Info                      : Audio Coding 3
Duration                         : 59mn 59s
Bit rate mode                    : Constant
Bit rate                         : 192 Kbps
Channel(s)                       : 2 channels
Channel positions                : L R
Sampling rate                    : 48.0 KHz
Video delay                      : -372ms

I decode the .tivo files after transfering them with Tivo Decoder http://tivodecode.sourceforge.net/

If I play the file with VLC, the first 10 seonds play at 720x480, then the window size jumps to 1920x1080 for the rest of the playback. VLC is the only player that I have come across that handles this correctly. MPC and WMP both will crash when the resolution switches.

I tried loading a file in VideoRedo, but when I move the selection slider to cut the first 10 seconds of the program I get an alarm popup titled Thumbnail Window Problem, with the error message: TN Video Thread: Video Dimensions changed. Clicking OK to the popup brings up the standard Windows crash dialog. The VideoRedo behavior is typical of the other editing programs I have tried, their thumbnail/preview window does not like the resolution change, which is why I tried using the command line mencoder.

[Megahurts]

You might try DVDPatcher on the decoded file.

Enter 1920 & 1080 for the custom horiz & vert size, 15.0MBit for bitrate and 29.97 NTSC for framerate.

Try Patch 'first header only' first. Check with MPC. If not working properly then Patch 'entire file'.

[olyteddy]

AVIDeMux might work for you too.

[TBoneit]

Have you tried the video redo option that lets you cut part of the video without opening it? I suggest going to the VideoReDo website then to their forums and ask there. They've always been very helpful. If they don't have a way right now to handle it I'd bet they work on that feature as HD broadcasts changing resolutions isn't a unknown phenomena.

[silentg]

Thank you all for the suggestions. I have found that if I demux the audio and video streams I can use Cuttermaran to chop off the initial 720x480 segment and then can remux the streams, but since that is a pain and isn't exactly quick to do on 5-10GB files, I will check into these latest ideas and let you know.

[silentg]

The solution ended up being a feature of Womble MPEG Wizard called MBS that will scan a MPEG file for multiple bitrate streams and allow you to add the streams you want to the timeline.

Thanks for all your help!