question about how to "Fix" non-standard mpeg2 files

[jimdagys]

I have a cheap TV card that outputs mpeg2 (file size 2GB per hour). The mpeg2 files play fine, but I have noticed, if I want to re-encode the mpeg2 files (for example to a lower bit rate), sometimes there is a problem during the encoding process. So I use the following procedure to "fix" the files, but I am wondering if there is a more direct way to "fix" the files.
1) I de-multiplex the mpeg2 file into video (m1v) and audio (mp2) files using TMPGEnc de-multiplex tool.
2) I input the video and audio file into Gui For DVD Author and make a temporary DVD
3) I use TMPGEnc DVD Author3 and use its extraction tool to extract the mpeg2 from the temporary DVD
4) Now I have the "fixed" mpeg2
Also, I am not sure what kinds of parameters get "fixed". Somebody in a previous post said something about "headers" but I don't understand that.

[manono]

Hi-

I have a cheap TV card that outputs mpeg2 (file size 2GB per hour).

I de-multiplex the mpeg2 file into video (m1v) and audio (mp2) files using TMPGEnc de-multiplex tool.

M1V is MPEG-1. Was that a typo? But there shouldn't be any problems with it as it's useable for DVD. The fact that Gui For DVD Author can work with it is the proof. You haven't said what problems you encounter during reencoding, or even how you reencode. If I had to guess, with no evidence at all to go by, I'd say the audio is non-DVD compliant 44,100 HZ, and you would only have to reencode it. Just a guess, though.

So, I wonder if they really need fixing. If I were to reencode, I'd frameserve using an AviSynth script file. And I bet you wouldn't have any reencoding problems and wouldn't have to use all those extra steps to get something you can use. To figure out what you have, you might open a cap directly in GSpot and post a pic here.

[olyteddy]

I started using PVA Strumento to demux my Hauppauge MPEG2 files after some of them choked when attempting to author them in ReJig.

Here's a log of what PVA Strumento does to my files:

***
***	PVAStrumento 2.1.0.17
***	  running at 01-08-2008 06:09
***
      Pre-Scanning input. May take some time.
Stream info for
C:\MyVideos\medium_4_1.mpg

Found 1 video stream.
Found 1 MPEG audio stream.

VIDEO #1
	Resolution 720 x 480 
	Aspect ratio is 4:3
	Frame rate 29.97 fps
	Nominal bitrate 7200000 bps
	First PTS: 00:00:00.333

MPEG AUDIO #1
	MPEG1, Layer 2
	stereo, sampled at 48.0 kHz.
	Bitrate 384 kbps
	Each frame contains 24.0 ms audio (1152 bytes)
	First PTS: 00:00:00.289

      
<<DEMUXING>>
      Input: C:\MyVideos\medium_4_1.mpg
      Options
      .. fixing stream synch.
      .. keeping track of audio offset accumulation.
      .. strict checking of audio framing.
      .. falling back to relaxed semantics on TS
      .. dropping GOPs longer than 980 KB
      .. splitting on change of video format.
      .. splitting on change of audio format.
      .. splitting on number of audio tracks.
      .. clearing CDF
      .. creating new GOP timecodes.
       
      Closing starting GOP.
      Aiming for sync at 00:00:00.333
      Cutting audio.
      Audio stream 1 now starts at 00:00:00.337
      Video stream 1 now starts at 00:00:00.333
      New MPEG video : F:\aaaa\medium_4_1_00.m2v
      New MPEG audio : F:\aaaa\medium_4_1_00 - DELAY 4ms.mpa
      Last fileset:
      	2434093660 total bytes written
      	Video 1: 112530 frames, 01:02:34.751
      	Audio 1: 157542 frames, 01:03:01.008
      
      Sync estimate at EOF:
      	 MPEG Audio #1 : sync
      
      Video statistics
      ================
         GOP length (min/avg/max):
                   15 / 15 / 15  [frames]
                   63710 / 300181 / 607394  [Bytes]
         GOP bitrate (min/avg/max):
                   1018 / 4798 / 9708 [kbps]
       

(Autosaving log to F:\aaaa\medium_4_1.txt)

The resulting M2V and MPA files author beautifully.

[halsboss]

I used PVAStrumento too, with mpeg2schnitt. Have replaced all with VideoRedo TV Suite ... bought it, one of the best things I've done.

[jimdagys]

Sorry, I didn't even realize(notice) that mpeg2 files when de-multiplexed yield m2v and mpeg1 files when de-multiplexed yield m1v. One problem I had when encoding with TMPGEnc is an error message when I get to the 50% encoding mark(using 2 pass VBR) . However, if I first "fix" the file, that solved solved that error message problem. I didn't save the error message so I don't remember what it was, except that the encoding was automatically terminated at the 50% mark. I'm not talking about error messages relating to audio sampling rate. I know the audio sampling rate must be at 48K.
I do have another question. If I have (for example) a 4GB mpeg2 file and want to reduce it to 1GB, is it better to convert the file to mpeg1 or leave it as mpeg2? It seems a lot of people here recommended mpeg1, but someone else said to use mpeg2, so I'm not sure which would give a better picture. I didn't even realize that mpeg1 and mpeg2 are different animals. I thought low bit rate mpeg2 was just called mpeg1.
Also, " frameserve using an AviSynth script file.is going to have to wait for another day because I have absolutely no idea about how to do that.

[manono]

Based on that log that olyteddy included, and on what he and halsboss said, I guess there can be problems with the video file capped with that card. And you're right; there's nothing wrong with that sampling rate.

As others have said to you, you can use MPEG-1 video in a DVD. DVD supports the MPEG-1 resolution. But VCD audio is 44,100HZ, whereas for DVD you need 48000HZ. So:

If I have (for example) a 4GB mpeg2 file and want to reduce it to 1GB, is it better to convert the file to mpeg1 or leave it as mpeg2?

If you're asking me, I wouldn't reduce a movie to 1GB. But if you're asking if it should be reduced to MPEG-1 resolution (352x288/240) for use in a DVD, or perhaps kept at full resolution (720x576/480), then my answer is it's going to look like garbage in any event; smoothed and blurry garbage at the lower resolution, or more detailed but blocky, smeary garbage at the higher resolution. I don't know; it's up to you. Try doing it both ways and see which looks the least bad to you. Maybe you watch on an old and small CRT TV set and it doesn't make much difference. After you get home and after you get a decent big screen TV set, you'll rue the day you ever got the bright idea of putting 4 movies on a single DVDR.

I thought low bit rate mpeg2 was just called mpeg1.

MPEG-1 has a specific resolution and bitrate for VCD. That same resolution and any bitrate can be used as a source for DVD.

[AlanHK]

Also, I am not sure what kinds of parameters get "fixed".

If GfD fixes them you can just mux the files the same way it does.

To see how GfD does this, after loading the video and audio files in GfD, click the "Make batch" button (not the "Create DVD" one).

It will create a bunch of files in its temporary folder.

One will be "batchrun0.bat".

If you look in it you will see something like this:

@echo off
echo.
echo (shrink and) mux video and audio files
"P:\GUI4dvdauthor\mplex.exe" -f 8 -o "q:\DVD\Temp\hr_117.mpg" "s:\mpg\hr_117.m2v" "s:\mpg\hr_117.ac3"

I.E., it uses the command line muxer "Mplex", installed under GfD, to mux your source files inot an mpg in the temp folder.

You can just run this file -- batchrun0.bat -- to create your MPEG.
Just change the filenames in it to run on any other files.

That should give the same result as extracting the MPEG from the VOBs.

Somebody in a previous post said something about "headers" but I don't understand that.

Restream is worth a try, it rewrites the header and timecodes.