Custom SAR / Stretch to Fit / better IMX50 support?

Hi, people. Nice community. Please excuse me for being a newbie here. I’ve only started using TVAI for a few weeks. That being said…


Of the two version I’ve tested (TVAI 3.2.6 and 4.1.0), cropping the input video does not affect the calculated SAR (appears to be calculated based on the stored DAR and resolution of the file). The result is a letterboxed output. Or, when Crop to Fill is selected, an output with pixels (valuable data) pushed outside the left and right of the screen. Both of which are undesirable.

Wouldn’t it be nice if TVAI can either:

  1. let users manually correct the SAR?
  2. support Stretch to Fit alongside Crop to Fill and Letterbox/Pillarbox?
  3. provide better support for the IMX50 format? (reason follows)

Related topics:


Back in the SD days when we digitize our 16:9 videos, we stored them in some 720x576 (5:4) files. The files have DAR set to 16:9, and the calculated PAR is 64:45 or 1.42:1 SAR (as detected by TVAI). When upscaling them to 1920x1080 (FHD) and with Square Pixel selected, TVAI is able to scale the videos correctly. No Letterbox/Pillarbox required at all.

However, we have some videos stored in the MXF-D10 (aka. IMX50) format, which for us in the 625/50 / PAL world (all pun intended), imposes a size of 720x608 (45:38). There are 32 extra lines at the top, which are just black. Below them are the actual video content 720x576 (5:4). These files also have DAR set to 16:9, but the calculated PAR is now 608:405 or 1.5:1 SAR (as detected by TVAI). We wouldn’t want the extra black lines in the final output so we used the cropping tool within TVAI and removed 32px from the top. The final output is letterboxed and I believe that it is because TVAI respects the calculated SAR of 1.5:1 even after cropping. Unfortunately in this case, that is not what we want.

MediaInfo recognizes the actual height is 576, and shows 608 as the “Original height”.

DaVinci Resolve also recognizes this and only displays the relevant portion of the video (720x576).

We looked into this and thought we might be able to trick TVAI into thinking the PAR is 1.42:1 by modifying the file DAR to compensate the effect of having 32 extra lines. Unfortunately, the ffmpeg command to set the DAR does not support arbitrary ratios.

Hence, we have the above Ideas.

Thanks for considering!

… that one is… crucial…

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