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Re: [HDTV-in-SFbay] Cozi Sherlock Holmes Postage Stamp aspect continues.

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  • Stephen H. Fischer
    Hi, I was able to download the documents. There is not sufficient time remaining in my life to understand much. Thanks. I am wondering if this guess is ~
    Message 1 of 30 , Feb 28, 2013
      

      Hi,

      I was able to download the documents. There is not sufficient time remaining in my life to understand much.

      Thanks.

      I am wondering if this guess is ~ correct,

      That the pixel shapes for the following resolutions is about the same:

      1920x1080 (16:9 program on 16:9 display)

      1280x720 (16:9 program on 16:9 display)

      704x480 (16:9 program on 16:9 display)

      704x480 (4:3 program on 4:3 display)

      > For some reason, the aspect ratio of non-square pixel

      > formats like 704x480 is very difficult for folks to understand.

      I think I am in that class, but then "string theory" is just as far beyond me.

      You do say non square, does that mean that the first two are square?

      I do have an idea of the "big bang" down very hot.

      Looking at your pictures I think that they were not helpful to me was because they did not show the additional black bands I am seeing.

      I was looking at a screen that is fixed in size with an additional black band and your pictures were wider than each other with out the additional black band.

      The document parts I scanned clearly show 704x480 in places. So that was not just stations guessing at a V and H.

      Finding two streams marked 704x480 (4:3) in addition to COZI's 704x480 (16:9) was a surprise.

      ------------------------------

      I now have a Magnum, P.I. Which the OP first complained about.

      It looks exactly like Sherlock Holmes does on Fusion with original ratio selected, an additional BLACK band on both sides. Selecting 16:9 Fixed produces a normal picture. MyHD and VLC Media Player also show a normal picture.

      So this problem is understood, an programming error in the tuner!

      SHF

       
       
      ----- Original Message ----- 
      Sent: Monday, February 25, 2013 7:22 PM
      Subject: Re: [HDTV-in-SFbay] Cozi Sherlock Holmes Postage Stamp aspect continues.

      All the ATSC specifications are free to download. A/53 is the
      main specification.

      http://www.atsc.org/cms/index.php/standards/standards?layout=default

      A/54A is also useful.

      http://www.atsc.org/cms/index.php/standards/recommended-practices

      However, the MPEG-2 specification is more useful in regards to
      aspect ratio. You can download an older version here which is
      entirely adequate for aspect ratio research.

      http://www.itu.int/rec/T-REC-H.262-199507-S/en

      For some reason, the aspect ratio of non-square pixel
      formats like 704x480 is very difficult for folks to understand.
      The use of pictures was an attempt to make it easier
      ("seeing is believing"), but it's difficult to know what's
      going to help for everyone.

      Ron

    • Ron Economos
      The pixel (sample) aspect ratio can be calculated like this (from section 6.3.3 of the MPEG-2 specification I linked to): sample aspect ratio = display aspect
      Message 2 of 30 , Mar 1, 2013
        The pixel (sample) aspect ratio can be calculated like this (from
        section 6.3.3 of the MPEG-2 specification I linked to):

        sample aspect ratio = display aspect ratio * horizontal size / vertical size

        So for 1920x1080 at 16:9 it would be:

        (9/16) * (1920/1080) = 1 (square pixels)

        For 704x480 at 16:9 it would be:

        (9/16) * (704/480) = 0.825 (non-square pixels).

        The typical way to test aspect ratios is to use a test pattern
        with circles. Any distortion can be easily seen. Here's a
        few bitstreams I created with a hardware MPEG-2 encoder.

        1) 720x480 at 16:9, just like Cozi is sending except 720 wide instead of 704

        http://www.w6rz.net/aspect16x9.ts

        2) 544x480 at 16:9, just to see how the decoder handles it. 544 wide is a
        valid MPEG-2 resolution.

        http://www.w6rz.net/aspect16x9_544.ts

        3) 720x480 at 4:3 with a display extension for 16:9. Again, just to see
        how the decoder handles it. A compliant decoder should display a
        16:9 image even though the aspect ratio is signaled as 4:3. Most
        (but not all) versions of VLC will do the correct thing.

        http://www.w6rz.net/aspect16x9_ext.ts

        All clips are about a minute long and about 144 Megabytes. Audio
        is silent. Have fun!

        Ron

        On 2/28/2013 10:00 PM, Stephen H. Fischer wrote:
         

        Hi,

        I was able to download the documents. There is not sufficient time remaining in my life to understand much.

        Thanks.

        I am wondering if this guess is ~ correct,

        That the pixel shapes for the following resolutions is about the same:

        1920x1080 (16:9 program on 16:9 display)

        1280x720 (16:9 program on 16:9 display)

        704x480 (16:9 program on 16:9 display)

        704x480 (4:3 program on 4:3 display)

        > For some reason, the aspect ratio of non-square pixel

        > formats like 704x480 is very difficult for folks to understand.

        I think I am in that class, but then "string theory" is just as far beyond me.

        You do say non square, does that mean that the first two are square?

        I do have an idea of the "big bang" down very hot.

        Looking at your pictures I think that they were not helpful to me was because they did not show the additional black bands I am seeing.

        I was looking at a screen that is fixed in size with an additional black band and your pictures were wider than each other with out the additional black band.

        The document parts I scanned clearly show 704x480 in places. So that was not just stations guessing at a V and H.

        Finding two streams marked 704x480 (4:3) in addition to COZI's 704x480 (16:9) was a surprise.

        ------------------------------

        I now have a Magnum, P.I. Which the OP first complained about.

        It looks exactly like Sherlock Holmes does on Fusion with original ratio selected, an additional BLACK band on both sides. Selecting 16:9 Fixed produces a normal picture. MyHD and VLC Media Player also show a normal picture.

        So this problem is understood, an programming error in the tuner!

        SHF

      • Stephen H. Fischer
        Hi, Fusion with 16:9 Fixed showed all three clips at full width on my 16:9 screen When I switched to Original Ratio 3) had the BLACK bands added to each
        Message 3 of 30 , Mar 1, 2013
          
          Hi,
           
          Fusion with "16:9 Fixed" showed all three clips at full width on my 16:9 screen
           
          When I switched to "Original Ratio" 3) had the BLACK bands added to each side and the circles were not round.
           
          My new 6 - Million Dollar Man Eyes could not really tell any difference with "16:9 Fixed" between the three.
           
          If you have a FTP for uploads, send me a PM with password, I captured an interesting KGO test pattern long ago. (3/6/2006) It's 39 MB in size.
           

          mailto:a_nani_mouse@...

          SHF
          ----- Original Message -----
          Sent: Friday, March 01, 2013 4:49 PM
          Subject: Re: [HDTV-in-SFbay] Cozi Sherlock Holmes Postage Stamp aspect continues.

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