Scanline corruption on FFmpeg videos
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#623 Scanline corruption on FFmpeg videos
I am using VICE 2.4.18, rev 29455M compiled with --enable-static-ffmpeg and --enable-gnomeui. This version of VICE can be used to record a video using the "Save media file…" command of the "Snapshot" menu.
The videos produced by this version of VICE often have their first and last few scanlines corrupted. That is, the first few and last few horizontal lines of the videos are replaced with garbage pixels. (Usual the pixels have random colours but sometimes they're all one colour.) The exact number of garbled scanlines seems to vary with the model of the emulated machine; for NTSC Commodore 64s, for example, VICE records videos at a resolution of 384×256, of which the top four and bottom six scanlines are always corrupted.
The problem doesn't seem to be specific to any one media container format or video codec; all the ones I tested had this problem.
Attached is a screenshot showing a recording of an NTSC C64.
this is probably expected when trying to encode a buffer whose dimensions are not a multiple of 8 (or 16?) - something for the ffmpeg expert(s) to fix :)
Fixed in rev 29512. Please comment if you prefer cutting (which is imlement now) or adding black border to get the %16 size.
I prefer cutting as long as it's done losslessly.
in windows, i get black only borders even without this fix.
Last edit: Querino 2015-03-22
Picture buffer may sometimes be clean (filled with 0) at allocation time, sometimes not. I saw the garbaged pixels even in windows.
ok, i was just lucky then. :)
it looks like it's "cutting" now. it works fine here.
only very minor cosmetic issue: the status bar (if shown) in the SDL version gets partially cut too. doesn't worry me personally.
I retested this with VICE 2.4.18, rev 29533 and can confirm that the garbage pixels are gone, at least with x64. NTSC C64s now record at 384×240.