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  1. A bit rate of 50 Mbps at 1920 x 1080 @ 30 interlaced frames/60 fields is equal to how many Mbps at 1280 x 720 @ 60 progressive frames?
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  2. You can not say that in general, it depends on the used codec, GOP settings, ...
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  3. Originally Posted by chris319 View Post
    A bit rate of 50 Mbps at 1920 x 1080 @ 30 interlaced frames/60 fields is equal to how many Mbps at 1280 x 720 @ 60 progressive frames?
    If the source is true 60 images per second video, for a given codec the bitrate requirements are usually similar. For film based material the 720p version can use significantly lower bitrate because most of the frames are duplicates.
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  4. it depends on the used codec, GOP settings, ...
    Those things being equal. The only things that change are 720/1080, interlace/progressive.
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  5. You cannot say exactly, is it camcorder video? That tends to be sharp with more details or lots of movement. Deinterlace method can save some bits too, like qtgmc or yadif (qtgmc deinterlace files end up a bit smaller but it is extremely slower), downscale method also matters I guess, here Spline36Resize was used. It is not 60i but 50i but as an example,
    avchd 50i.M2TS 118MB
    fullHD 50i from avchd.mkv 117MB
    QTGMC_then_downscale_to_720p50.mkv 49MB
    Yadif_then_downscale_to_720p50.mkv 55MB
    So for camcorder video with movement I got fullHD interlaced to 720p50 ratio something between 2/1 to 3/1
    For camcorder videos this bob downscale is is a not bad choice for delivery, it is progressive, size is smaller and it looks ok, camcorders do not have full 1080 true resolutions anyway.
    Last edited by _Al_; 18th Oct 2018 at 19:52.
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  6. Keep in mind that x264 in CRF mode uses lower quality (higher average quantizers) with higher frame rates (on the theory that you are less likely to see artifacts at higher frame rates). If it didn't do that the 720p50 video would have been more like 75 MB. Some (most?) other encoders aren't frame rate aware like this.

    1080i25 is 1920x1080x25 = 51.8 million pixels per second. 720p50 is 1280x720x50 = 46.1 million pixels per second. So 1080i is only about 12 percent more pixels per second than 720p.
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  7. Here is what I get for pixel count of the uncompressed image, 8-bit video * 3 channels.

    There are 30 complete images (2 interlaced fields) per second interlaced; 60 per second progressive.

    I'm trying to arrive at a ratio between 1080i and 720p, not absolute values.

    Code:
    Interlaced	
    X	1920
    Y	1080
    Complete frames (not fields)	30
    Bits per pixel	24
    	1,492,992,000
    	
    Progressive	
    X	1280
    Y	720
    Complete frames (not fields)	60
    Bits per pixel	24
    	1,327,104,000
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  8. There's no simple relationship between birate requirements and frame size. It depends on the nature of the individual video, scaling algorithms, etc.

    By the way most "video" isn't 24 bits per pixel -- it's most often 12 bits per pixel with YUV 4:2:0 chroma subsampling (DVD, Blu-ray, youtube, etc.).
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  9. It depends on the nature of the individual video, scaling algorithms, etc.
    As I said earlier, those things are being held constant.

    By the way most "video" isn't 24 bits per pixel -- it's most often 12 bits per pixel with YUV 4:2:0 chroma subsampling (DVD, Blu-ray, youtube, etc.).
    As I also said, were considering uncompressed video, i.e. 4:4:4.
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  10. Member Bernix's Avatar
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    Hi,
    you are closest to try it. You have to first deinterlace and then resize. So can't see problem encode both at once probably or one then another. You can try pick part of video for example 3mins and test both at same CRF. Probably you will find that difference isn't as big as you expected. Deinterlace will took enough time. So you deinterlace at FullHD level to invent another half of content, and then through it away with scaling down? Seems to me big ratio of invented material than actually recorded.



    Simply it seems to me not be right made up another 60 FullHD fields and then throw away more than 1/2 of information resizing it. At least to keep FullHD progresive 60FPS that you get as some sort of backup. Once you are there and only problem is encoding it.


    P.S. lots of rewritten things here, have not power to read it again. Probably will give someone some sense.

    Edit: you are asking for bitrate probably because of intention of streaming it. So CRF isn't your friend. You also if you want to stream really stream to cap max bitrate according to your needs.
    Nba is transmiting they VR content just front hemisphere and you need at least 20Mb/s internet connection. And quality isnt superb, can be far much better. But also to cover front hemisphere of view bigger resolution is needed.


    Bernix
    Last edited by Bernix; 19th Oct 2018 at 11:07. Reason: Edit
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