Best Batch Conversion Tool for Windows?

[pone44]

I am looking for a tool that I can use to batch convert webp files into GIF format.

A second requirement - which could be a separate tool if necessary - would be the ability to draw a region within an MP4 file and then have a new MP4 created that is within the drawn region.

What are the best tools for these requirements that work under Windows? I saw a utility named xnConvert that looks promising. But I want to get feedback on all tools before I invest time in this.

[bolide]

ImBatch is a great and free batch image processing tool, and it supports .webp and gif (including animated gif), but it doesn't work with video files.

I am not completely clear with your MP4 task, so I cannot suggest on this, sorry

[pone44]

For the batch conversion of animated WEBP to GIF I went with reaconverter. This is not freeware but has a very clean and functional interface.

[pone44]

I am not completely clear with your MP4 task, so I cannot suggest on this, sorry

It is not that common of a case, but sometimes someone will take a video with the camera in a fixed position, and they have composed the scene incorrectly. I want to be able to draw a rectangle around the area of interest and rewrite the video based on that drawn rectangle.

[abolibibelot]

It is not that common of a case, but sometimes someone will take a video with the camera in a fixed position, and they have composed the scene incorrectly. I want to be able to draw a rectangle around the area of interest and rewrite the video based on that drawn rectangle.

Any non-linear video editor (commonly abbreviated as NLE) should allow to crop and/or rotate a whole video and then re-export it ; it's quite trivial in the grand scheme of video editing things.
It could be done with Avisynth as well. I made the following script recently to fix that mess (see at 01:03 after the end of the opening -- the other episodes are fine) :

V = FFVideoSource("T and T episode 34 [-f 137+140].mp4")
V1 = V.Trim(0,1900).BicubicResize(1280,720)
V2 = V.Trim(1901,39383).Crop(528,300,-528,-300).BicubicResize(1280,720)
V3 = V.Trim(39383,0).BicubicResize(1280,720)

V1 ++ V2 ++ V3

Then made this ffmpeg script to encode the result :

chcp 1252
ffmpeg -i "T and T episode 34 [-f 137+140].mp4 v2.avs" -i "T and T episode 34 [-f 137+140].mp4" -map 0:0 -map 1:1 -c:v libx264 -crf 20 -preset veryslow -c:a copy "T and T episode 34 [-f 137+140] corrigé.mp4" >"T and T episode 34 [-f 137+140].mp4 ffmpeg.txt" 2>&1
pause

Since I downloaded all the other episodes in 1280x720, and used the 1920x1080 version as the source to fix that one, and used a rather high quality -crf setting, and since it's an old show with a rather soft picture to begin with, the resulting file, which is in the same ballpark as the others size-wise (216MB for 22 minutes), is practically undistinguishable from the others from a picture quality standpoint (other episodes have actually a far softer picture, resulting in them having a much lower size for a similar duration, ep. 48 for instance has a size of 150MB in 1280x720 for a duration of 21:34).

A graphic NLE software is more cumbersome to install and to launch, but might be easier to use for a beginner. The quality of H.264 encoding produced by x264 is usually reported to be significantly better at a given bitrate than what the encoder embedded with those pieces of software (usually from Mainconcept) tends to produce. A workaround to get the benefit of a higher quality / size ratio is to export from the NLE in a lossless format (Lagarith, UT Video, MagicYUV and so forth), then encode with ffmpeg / libx264 or any GUI program relying on either ffmpeg or x264 to encode video streams, of which there are approximately a gazillion and a half.
In-between, more simple graphic editors like VirtualDub2 or Avidemux should be able to perform such a simple picture processing and recompress with x264 in a single step with less hassle.