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  1. In VirtualDub, where is the capture BITRATE setting?

    In my previous VHS capture software (PotPlayer), one of the to-be-designated capture settings was “BITRATE”. For capture of VHS video, I set this to 8000 kbs.

    I’m just learning VirtualDub. In capture mode, I cannot find where to set capture bitrate. (Note: I do not refer to the frame rate (29.97), but bitrate.)

    In terms of VirtualDub, am I missing something or doing things incorrectly?

    Thank you.
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  2. Member
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    There is no setting on lossless codecs
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  3. Thank you. I did not know that.

    By the way, suppose in my learning and testing VirtualDub I had, for example, opted to capture as codec H.264. Would one of the dialogs in VirtualDub's Capture Mode then asked for the bitrate at which to capture?

    Thank you.
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    h264 is a delivery format.. always capture lossless, edit and convert after
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  5. Ok. Shall do.

    Thanks.
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  6. Originally Posted by smartel View Post
    h264 is a delivery format.. always capture lossless, edit and convert after
    h264 can be lossless too - when encoding using lossless profile
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  7. Member dellsam34's Avatar
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    Originally Posted by poisondeathray View Post
    Originally Posted by smartel View Post
    h264 is a delivery format.. always capture lossless, edit and convert after
    h264 can be lossless too - when encoding using lossless profile
    Can you elaborate a little bit on that? Do you mean by lossless in terms of bitrate or chroma subsampling? One more question about chroma sub, Is it common to use 4:2:2 in h.264 with compressed files for captured SD files? Sorry didn't mean to hijack the thread.
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  8. Originally Posted by dellsam34 View Post
    Originally Posted by poisondeathray View Post
    Originally Posted by smartel View Post
    h264 is a delivery format.. always capture lossless, edit and convert after
    h264 can be lossless too - when encoding using lossless profile
    Can you elaborate a little bit on that? Do you mean by lossless in terms of bitrate or chroma subsampling? One more question about chroma sub, Is it common to use 4:2:2 in h.264 with compressed files for captured SD files? Sorry didn't mean to hijack the thread.

    "Lossless" can only mean one thing . It's a binary yes or no classification. When decoded/decompressed , the input and output are identical in every way . You can measure PSNR , look in a hex editor, measure differences (e.g. 2 layers in an editor in subtract or difference mode)

    A difference in chroma subsampling, by definition means it's not lossless

    In the uncompressed state, bitrate will always be the same, because they are the same pixel format. Same bit depth, same color model (e.g. YUV vs. RGB) , same chroma subsampling

    In the compressed state, the lossless compressed bitrate can be very different. You can use higher compression (smaller filesizes, more difficult to decode/encode) , or lower compression (higher filesizes, easier to encode/decode). Long GOP lossless (temporal compression) can easily produce files 1/2 the size of huffyuv or lagarith . But for capture, people tend to go with intra compressed (I frame only) formats, because it's less likely to drop frames, and it's easier for real time capture . You can choose just about anything, any combination with AVC/h264, it's a very versatile format

    4:2:2 is common for SD capture, regardless of format choice. The main issue is how some other programs handle interlaced chroma , add 4:2:2 avoids many of the issues. It usually has nothing to do with the actual quality , or measurable line pairs of chroma information resolvable detail

    h264 is less common for capture in the past, because of higher encoder/decoder requirements. It's perfectly fine for SD on a computer less than 10 years old. Basically a dual core is safe.
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  9. Dinosaur Supervisor KarMa's Avatar
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    I capture VHS with 4:2:2 - interlaced - x264 regularly. I don't even use it for lossless, as x264 lossless isn't even the best out there. But it's good at lossy and modern CPUs can handle it.
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  10. Note: When you do use an encoder with a bitrate setting it's in the encoder's configuration dialog: Video -> Compression... -> select encoder -> Configure button.
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  11. Thank you, jagabo.

    I just looked and noticed that several of the codecs listed in the dialog (for VirtualDub2) do indeed have a field (at the bottom right) for specifying a capture bitrate. Other of the codecs present a configuration dialog having many options, none of which I yet understand. Bu contrast, the configuration dialog for huffyuv and lagarith are simple as can be.

    Glad to know where the quality and bitrate variables are located in case they become relevant.

    Thanks again.
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    What is the ramification of capturing interlaced fields to a progressive H264?
    Since the encoder treated the source as progressive, my first thought is that the encode
    is compromised in some way.
    You can still separate the fields, but what about the overall integrity of the encode?
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  13. Originally Posted by davexnet View Post
    What is the ramification of capturing interlaced fields to a progressive H264?
    With a 4:2:2 source and 4:2:2 encoding nothing will be wrong. With a 4:2:0 source (or 4:2:2 source converted to 4:2:0) the chroma of the two fields will be blurred together. It's visible as ghosting of the colors when you view still frames.
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    Originally Posted by jagabo View Post
    Originally Posted by davexnet View Post
    What is the ramification of capturing interlaced fields to a progressive H264?
    With a 4:2:2 source and 4:2:2 encoding nothing will be wrong. With a 4:2:0 source (or 4:2:2 source converted to 4:2:0) the chroma of the two fields will be blurred together. It's visible as ghosting of the colors when you view still frames.
    Thank you jagabo
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