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#1 | Link |
Registered User
Join Date: Dec 2008
Posts: 19
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Transcode from Motion JPEG AVI to I-frame-only MPEG-1
Is it doable? Is a motion-jpeg frame identical to an MPEG-1 i-frame? If so, is there any utility that will losslessly rip each jpeg frame and place it in MPEG?
The best I could find was here http://forums.maxconsole.net/showthread.php?t=6089 which referred to code here http://www.codeproject.com/KB/graphi...GFunction.aspx Unfortunately the code and the demo program are gone. Also I don't even know if the demo program could do what the thread title says (convert Motion JPEG AVI to I-frame-only MPEG-1) or if was only meant to convert one frame. Also is this doable with MPEG-2? or MP4? |
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#2 | Link |
Registered User
Join Date: Oct 2004
Location: India
Posts: 321
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doable with TMPGEnc. MPEG Settings-GOP structure- Iframes only. With mp4 codecs, max keyframe interval=1. You will need to set quality based encoding at close to 100% quality.
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#3 | Link |
Registered User
Join Date: Dec 2008
Posts: 19
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Before I made the post I had already tried with TMPGEnc, I-frame only. My intuition told me it would recompress, not losslessly transcode, and I was right. So I don't think that works. Here's how I know: the output differs wildly in size. It shouldn't if it were a lossless transcode (just difference in overhead for container change which tends to be minimal).
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#5 | Link |
Moderator
![]() Join Date: Oct 2001
Posts: 3,530
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I've been holding back while trying to locate a program I found years ago and tucked away to look at later, but can't locate it in my files or online. Someone did write a program to do this, although I believe it was to mpeg-2 not mpeg-1.
As Dark Shikari noted jpeg and mpeg both use 8x8 DCT compression. Both also allow for custom quantization. However there are two areas which present problems. 1) Jpeg allows 4 types of chroma subsampling but mpeg allows only 3: no subsampling (4:4:4) horizontal subsampling (4:2:2) both horizontal and vertical subsampoling (4:2:0) So for all except vertical only subsampling the image data can be left intact. For vertical only subsampling you would have to either upsample to 4:4:4 or downsample to 4:2:0 2) jpeg allows interlacing which is not supported at all in mpeg-1, and not equivalent to mpeg-2 field interlacing. These images would have to be fully decoded and re-encoded. |
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Tags |
i-frame, mjpg, motion jpeg, mpeg-1, transcode |
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