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A comment on FFmpeg Drawtext Filter for Overlays, Scrolling Text, Timestamps on Videos. Parent comment

Re:FFmpeg Drawtext Filter for Overlays, Scrolling Text, Time... by twic on Friday October 23, 2020 @04:44AM (#24867266)
> Burning subtitles into the video implies re-encoding

In principle, would it be possible to only re-encode the macroblocks affected by the subtitles, leaving the rest of the frame bit-for-bit identical?

It's been a long time since i read a video encoding specification, so i don't know if things still work this way.

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Re:FFmpeg Drawtext Filter for Overlays, Scrolling Text, Time... by beagle3 on Friday October 23, 2020 @05:52AM (#24867671)
Much harder than it sounds because future macroblocks depend on present ones, and motion vectors mean that over a few seconds, transitive dependency can reach the entire image (and does in panned and zoomed shots)

Can possibly work, but depending on movie content might not save all that much encoding.

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Re:FFmpeg Drawtext Filter for Overlays, Scrolling Text, Time... by _Gyan_ on Friday October 23, 2020 @06:16AM (#24867850)
What would be much better would be to encode an overlay raster stream, which the player can then composite at runtime, like they do with text subtitles.

Much faster to encode. Can be toggled. But players need to support it.

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Re:FFmpeg Drawtext Filter for Overlays, Scrolling Text, Time... by danielheath on Friday October 23, 2020 @09:01AM (#24869000)
Yeah, but the whole point of the exercise is to see subtitles on players that don't even support subtitles; they're definitely not going to support an overlay stream.
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