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I have an interlaced video with MTS file format, which was captured using a HD camera. When I play it using VLC, it is displayed at resolution 1920x1080 and if I take a snapshot with VLC, the saved image also has a resolution of 1920x1080. I tried playing the video with the Windows Media Player, and the video is also rendered at a resolution of 1920x1080.

However, in VLC, when I select Tools > Codecs information I get the following :

Type: Video
Id original: 4113
Codec: H264 - MPEG-4 AVC (part10) (h264)
Resolution: 1440x1080
Framerate: 25
Decoded format: Planar 4:2:0 YUV

(there also are an audio stream and a subtitle stream, which I am not interested in).

So the exposed resolution seems to be 1440x1080 but when rendered the video is 1920x1080.

Anyway, my true problem comes from the fact that I need to extract the frames from the video to perform some Image Processing. I do that using ffmpeg, which extracts frames at the resolution of 1440x1080, but then the extracted images seem distorted (i.e. compressed horizontally), which causes errors for the Image Processing I am doing.

Any idea why VLC, Windows Media Player, Power DVD manages to render the video correctly, whereas ffmpeg fails to extract the frames at the correct resolution ? And why is the video rendered at 1920x1080 if the exposed codec resolution is 1440x1080 ?

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HDV camera, right? It's not untypical for cameras to claim higher resolution than they actually scan. In such cases you have to look at the different aspect ratios involved: pixel, frame, display, sample. Here's a post that discusses this, or google "HDV aspect ratio". And here's a link to the spec from the HDV consortium.

It's essentially anamorphic. The ffmpeg or avconv docs should show how to extract and expand to 1920 in one step.

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    The specs for HDV are listed here. You'll see that the frame is indeed anamorphic. You could use vf scale=1920:1080,setsar=1:1 to ensure the output is full raster (though it will be interpolated).
    – stib
    Aug 27, 2015 at 0:32
  • Thanks for both your explanations. I checked in ffmpeg and it is indeed saying the following about the input video stream: Video: h264 (High) (HDMV / 0x564D4448), yuv420p, 1440x1080 [SAR 4:3 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc. @stib I am not familiar with the anamorphic term, but ultimately, I would like to recover the image as captured by a pinhole camera model. Do you know if the ffmpeg video filter vf scale=1920:1080,setsar=1:1 is enough for that ?
    – BConic
    Aug 27, 2015 at 7:37
  • Yes, that filter chain should suffice.
    – Gyan
    Sep 19, 2015 at 13:13

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