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Re-encoding MPEG2 CBR to lower bitrate

 
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gzp



Joined: 08 Mar 2004
Posts: 3
Location: Budapest, Hungary

PostPosted: Mon 8 Mar 2004, 0:47    Post subject: Re-encoding MPEG2 CBR to lower bitrate Reply with quote

I was captured some TV show with a Hauppauge PVR350 card in PAL 720x576 25fps at 16000kbps bitrate CBR. After 2h or recording got a 15GB file, but my plan was to capture at 16mbit and later reencode it in 2pass VBR with a software. The captured file was really good quality, sound is mp2 at 384kbps.

Tried TMPGEnc Plus to do the job, first used the PAL DVD template, running 2pass VBR at avg 8kbit, but I was unable to get back the quality I captured. The big motions were squared. Read the FAQ, and skipped the wizard. :-)

Tried everything, even encoding in CBR 14mbit, but I can't produce the same quality I have.

Also tried to record with the card at lower bitrate like 8, and until 3mbit the quality is acceptable.

So I have 4x15GB mpeg2 recorded with cbr 16mbit, and currently I'm unable to reencode it to fit at least 50 minute to a DVD-R.

Could anybody help with some tip I should try? Or provide more info about the parts of project.
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RMN
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Joined: 04 Feb 2003
Posts: 587
Location: Lisboa, Portugal

PostPosted: Mon 8 Mar 2004, 15:24    Post subject: Reply with quote

Recompressing MPEG-2 always introduces a quality loss. One of the problems is that TMPGEnc doesn't have its own MPEG-2 decoder, and instead uses the one installed in the system. If this decoder degrades quality, then TMPGEnc's source will have low quality to begin with, and after TMPGEnc encodes, it'll look even worse.

Also, naturally, at 8 Mb/s, you can't get the same quality as with 16 Mb/s. But you should be able to get pretty good quality anyway, especially if the source is good.

I suggest trying to capture directly at 8 Mb/s and seeing if the quality is better than the one you get by capturing at 16 Mb/s and then recompressing the file through TMPGEnc.

Also, please post the exact settings you used in TMPGEnc.

RMN
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gzp



Joined: 08 Mar 2004
Posts: 3
Location: Budapest, Hungary

PostPosted: Mon 8 Mar 2004, 15:44    Post subject: Reply with quote

Seems like the key is here the already installed mpeg2 decoder which comes with the XP. Its a fresh install, no other program installed to avoid mess.

I have tried already to capture at 8mbit, even at 5mbit, but the produced output is always worse than the original file.

Anyway, I have found that capturing at 5mbit will serve my future needs, and I'll be able to save 2 episodes per DVD-5, but I still have 5x15GB stream at 16mbit which means even a half episode can't fit on a DVD-5, so I would like to do something.

Maybe I should use another tool to do the job, or install a third party coded?
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neil wilkes



Joined: 26 Dec 2003
Posts: 51
Location: London, England

PostPosted: Mon 15 Mar 2004, 17:57    Post subject: Reply with quote

Try capturing to DV AVI instead of compressed MPEG-2, and then encode to MPEG using TMPGEnc?
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gzp



Joined: 08 Mar 2004
Posts: 3
Location: Budapest, Hungary

PostPosted: Mon 15 Mar 2004, 18:14    Post subject: Reply with quote

Could you explain why to DV AVI?
Anyway this is a hw mpeg2 encoder, I don't think I'm able to capture in AVI.
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