ffmpeg 从cropdetect 中获取值

2021-12-26 00:00:00 ffmpeg php

是否可以在一行中运行cropdetect 和crop 并从视频中获取拇指?

Its possible to run cropdetect and crop in one line and get thumbs from video?

像这样

ffmpeg -ss 1 -i 0.flv -vf cropdetect=24:16:0,crop=w:h:x:y -vcodec mjpeg -vframes 1 -an -f rawvideo -s 240x180 0.jpg

或者可能需要在 2 行中运行，首先运行cropdetect，然后运行crop 并从视频生成拇指，但这样我需要从cropdetect 中获取价值?

Or maybe need to run in 2 line, first run cropdetect and than run crop and generate thumbs from video, but in this way i need to get value from cropdetect?

推荐答案

cropdetect 输出到控制台，因此您可以解析输出，然后将其用作变量:

cropdetect outputs to the console, so you can parse the output and then use it as a variable:

ffmpeg -i input -t 1 -vf cropdetect -f null - 2>&1 | awk '/crop/ { print $NF }' | tail -1

这将导致类似:

crop=640:480:0:50

然后运行您的实际裁剪命令:

Then run your actual crop command:

ffmpeg -i input -vf $cropvalue,scale=240:-1 -vframes 1 -qscale:v 2 output.jpg

  • -vcodec mjpeg、-an 和 -f rawvideo 是多余的

    使用-qscale:v控制jpg输出质量.合理的范围是 2-5(较低的值表示较高的质量).

    Use -qscale:v to control jpg output quality. A sane range is 2-5 (a lower value is a higher quality).

    使用 scale 过滤器而不是-s;特别是如果您已经在使用过滤器.此外，scale 过滤器将允许您设置特定的宽度或高度，并且使用 -1 它将自动提供正确的值以保留方面.否则，如果您尝试强制使用特定大小，则可能会导致输出被压扁或拉伸.

    Use the scale filter instead of -s; especially if you're already using filters. Also the scale filter will allow you to set a specific width or height and with -1 it will automatically provide the correct value to preserve aspect. Otherwise if you try to force a specific size you can risk a squished or stretched output.

    显然我不是 PHP 编码员，但这至少应该给你一个想法.

    Obviously I'm not a PHP coder, but this should give you an idea at least.

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