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Track aspect ratio vs. DAR

awilkens
2013-02-25
2013-02-26
  • awilkens
    awilkens
    2013-02-25

    If the resolution of a digtital video is 720x486, I don't understand why the DAR is 3:2 and the video track aspect ratio is 1.481 (4:3). Is this because the pixels are rectangular and not square? or that when the video is played there are six lines being cut off in the display? Thanks in advance for any clarification you can provide. Ann

     
  • Difficult to understand your questions.
    Resolution and DAR are not related.
    You have:
    - Pixel resolution (e.g. 720x486)
    - DAR (e.g. 4:3)
    In the exceptional case that PAR (Pixel Aspect Ratio) is 1:1 width divided by height is your DAR, but it is not the rule for all files (when PAR is not 1:1 i.e. no square pixels, the formul is mor complex: DAR=Width/Height*PAR, you need 3 of theses values in order to know the geometry of your frame, if you have only 2, you don't know how the frame should be displayed).

    or that when the video is played there are six lines being cut off in the display?

    It depends of your player. The file is 720x486 with a specific DAR, then your player adapts the frame to your screen, it can put black bars on the screen, it can cut some lines, it can shrink or expand (awful, DAR is not respected) the frame to fit your complete screen, it is a decision of you or/and your player, nothing related to the file.

     
  • awilkens
    awilkens
    2013-02-25

    Maybe I should ask it this way... Why in the pbcore xml view does it say under the video heading that the track aspect ratio is 1.481 and the display aspect ratio is 1.481 but in the tree view is says the track aspect ratio stays the same but the display aspect ratio is 3:2? I was expecting the display ratio in one view to match in the other views. What am I missing?

     
  • 1.481 and the display aspect ratio is 1.481 but in the tree view is says the track aspect ratio stays the same but the display aspect ratio is 3:2?

    The default tree view use some "well known" values, with some rounding, for end users not wanting to have such precision (e.g. most users don't care of 1.789, but they like to see it is near 16:9). PBCore output has the exact (3 digit) value. You can have this value in the tree (or text) view if you check Debug --> Advanced mode menu.

    About difference between track aspect ratio and display aspect ratio, I don't understand, I don't use "track aspect ratio", please provide the output so we can talk about the same thing.

     
  • awilkens
    awilkens
    2013-02-26

    Thanks! The advanced mode gives me what I was looking for.

    "difference between track aspect ratio and display aspect ratio, I don't understand, I don't use "track aspect ratio"

    I should say "essence track aspect ratio"


    <pbcoreEssenceTrack>
    <essenceTrackType>Video</essenceTrackType>
    <essenceTrackIdentifier>1</essenceTrackIdentifier>
    <essenceTrackIdentifierSource>ID (Mediainfo)</essenceTrackIdentifierSource>
    <essenceTrackStandard>NTSC</essenceTrackStandard>
    <essenceTrackLanguage>eng</essenceTrackLanguage>
    <essenceTrackEncoding>YUV (2vuy)</essenceTrackEncoding>
    <essenceTrackDataRate>167808983 CBR</essenceTrackDataRate>
    <essenceTrackDuration>1701567</essenceTrackDuration>
    <essenceTrackFrameSize>720x486</essenceTrackFrameSize>
    <essenceTrackAspectRatio>1.481</essenceTrackAspectRatio>
    <essenceTrackFrameRate>29.970 CFR</essenceTrackFrameRate>
    <essenceTrackAnnotation>Count: 255|StreamCount: 1|StreamKind: Video|StreamKindID: 0|StreamOrder: 0|Inform: English, 168 Mbps, 720486 (3:2), at 29.970 fps, YUV (NTSC)|ID: 1|Format: YUV|Format_Commercial: YUV|CodecID: 2vuy|Codec: 2vuy|Codec/CC: 2vuy|Duration: 1701567|BitRate_Mode: CBR|BitRate: 167808983|Width: 720|Height: 486|PixelAspectRatio: 1.000|DisplayAspectRatio: 1.481|Rotation: 0.000|FrameRate_Mode: CFR|FrameRate: 29.970|FrameCount: 50996|Standard: NTSC|ColorSpace: YUV|ChromaSubsampling: 4:2:2|ScanType: Interlaced|ScanOrder: BFF|Compression_Mode: Lossless|Bits-(PixelFrame): 16.001|Delay: 3581515|Delay_Settings: DropFrame=Yes / 24HourMax=No / IsVisual=No|Delay_Source: Container|StreamSize: 35692304384|StreamSize_Proportion: 0.99054|Language: en|Encoded_Date: UTC 2013-02-12 17:18:58|Tagged_Date: UTC 2013-02-12 17:18:59|colour_primaries: BT.601 NTSC|matrix_coefficients: BT.601</essenceTrackAnnotation>
    </pbcoreEssenceTrack>

     
    Last edit: Jerome Martinez 2013-02-26
  • awilkens
    awilkens
    2013-02-26

    My example doesn't include the fields. I'll try again later...

     
    • awilkens
      awilkens
      2013-02-26

       
  • I reformated your text, XML is undertood as something else by Sourceforge editor.

    essenceTrackAspectRatio is 1.481, it is the value of DAR.
    I don't see the difference you are talking about: in all cases, it is 1.481 (PBCore essenceTrackAspectRatio or defaut MI output DisplayAspectRatio).