Edit, enhance and archival encode of MPEG-2 M2T container files
 

I've been transferring VHS video from a JVC HM-DH40000U using the Firewire interface directly to hard drive. The result is a M2T file that contains MPEG 2 video and then what appears to be MPEG 1 audio and another audio track which is PCM. The video is 480i NTSC 720 X 480 pixels.

I've done some research on this type of container and format and there isn't much info out there even though it doesn't seem too odd for a digital video format of that era?

What I'm having problems figuring out is the following:

• How to losslessly edit the M2T files (or do they need to be converted first?)
• What archival format to convert them to.

I've had limited success using AVIDemux, but I don't think that can import the PCM audio which I think is the higher quality of the two. I also think AVIDemux won't allow me to do simple editing without converting first? I'm less concerned about what archival format we end up with as long as it's not generating digital artifacts and it's not something proprietary. MPEG-2 broadcast or DVD maybe since the source is only 480i? The files are straight captures of entire tapes, so I'm not sure if there are timecode markers where the control track drops? If so, that might be handy for finding "chapters".

As far as enhancement, I think I can find most of that info here (like removing head switching) but first I need to learn to walk. :wink2:

Here's the MediaInfo on the files I'm working with:

General

ID : 1 (0x1)

Complete name : Sample.m2t

Format : MPEG-TS

File size : 24.2 MiB

Duration : 16 s 297 ms

Overall bit rate mode : Constant

Overall bit rate : 12.4 Mb/s

Maximum Overall bit rate : 12.4 Mb/s

Video

ID : 4096 (0x1000)

Menu ID : 1 (0x1)

Format : MPEG Video

Format version : Version 2

Format profile : Main@Main

Format settings, BVOP : Yes

Format settings, Matrix : Custom

Format settings, GOP : M=3, N=15

Format settings, picture structure : Frame

Codec ID : 2

Duration : 16 s 250 ms

Bit rate mode : Constant

Bit rate : 9 550 kb/s

Width : 720 pixels

Height : 480 pixels

Display aspect ratio : 4:3

Frame rate : 29.970 (30000/1001) FPS

Standard : NTSC

Color space : YUV

Chroma subsampling : 4:2:0

Bit depth : 8 bits

Scan type : Interlaced

Scan order : Top Field First

Compression mode : Lossy

Bits/(Pixel*Frame) : 0.922

Time code of first frame : 00:00:05;00

Time code source : Group of pictures header

GOP, Open/Closed : Open

Stream size : 18.3 MiB (76%)

Audio #1

ID : 4098 (0x1002)

Menu ID : 1 (0x1)

Format : MPEG Audio

Format version : Version 1

Format profile : Layer 2

Codec ID : 3

Duration : 16 s 224 ms

Bit rate mode : Constant

Bit rate : 384 kb/s

Channel(s) : 2 channels

Sampling rate : 48.0 kHz

Compression mode : Lossy

Delay relative to video : -172 ms

Stream size : 761 KiB (3%)

Audio #2

ID : 4100 (0x1004)

Menu ID : 1 (0x1)

Format : PCM

Format settings, Endianness : Little

Muxing mode : SMPTE ST 302

Codec ID : 131

Duration : 16 s 249 ms

Bit rate mode : Constant

Bit rate : 1 536 kb/s

Encoded bit rate : 1 920 kb/s

Channel(s) : 2 channels

Sampling rate : 48.0 kHz

Bit depth : 16 bits

Delay relative to video : -220 ms

Stream size : 2.98 MiB (12%)

Menu

ID : 110 (0x6E)

Menu ID : 1 (0x1)

List : 4096 (0x1000) (MPEG Video) / 4098 (0x1002) (MPEG Audio) / 4100 (0x1004) (PCM)

Maximum bit rate : 12440000

M2T = M2TS = MPEG-2 Transport Stream. It's the same container format used by Blu-ray, but most discs stuff AVC video and lossless audio into that container.

There are some free tools for editing MPEG-2 streams as losslessly as possible. You'd have to do searches, as I dunno what they are myself. Most will only do cuts at the GOP level, or they will re-encode the whole file. Your GOP is 0.5 sec, so if you are happy with having a little slack or over-trimming, GOP editing would be fine.

The best editors will cut at the GOP level, then re-encode only the few frames necessary to perform your frame-accurate edit. Womble and VideoReDo are the most highly rated ($$).

"Enhancing" these files isn't such a good idea, since they are already in a delivery format, not an editing format. You'll have some compounding compression artifacts even if you way overshoot the existing bitrate on your re-encoding.

Any alteration of the image requires lossy re-encoding. As noted earlier, final delivery formats are lossy inter-frame encodes not designed for alteration. Here's an article that explains why, with somewhat limited information on a few "editing" formats: http://telestreamblog.telestream.net...hen-editing-2/.