video editing mistakes

get it right


divx logo
black borders on the sides

divx logo

Have you ever noticed a divx logo in the bottom right of videos? It happens a lot - it seems almost all AMV's on youtube have them, for example. Search for AMV on it.

logo in amv on youtube

How it gets there: the divx codec, by default, inserts it into it's decoder output. So people use divx with the logo enabled, and edit (decode, cut, re-encode) videos, and this way the logo gets into everything they create. While divx only shows the logo in the begin, if you cut pieces of video it shows in every piece again, so you see it during the entire AMV. If you use the registered version, you can disable the logo, otherwise you can't. So people editing videos either use the demo version of divx, or they simply don't think about disabling the option. To disable it: start menu -> programs -> divx -> divx codec -> decoder configutration utility.

option in divx control panel

If you have the demo version of divx, you have 2 choices. 1: Get the registered version, 2: Get xvid, a program which is free, and can decode and create divx compatible videos, without any demo restrictions. If you installed xvid, you can use this guide to configure it to produce videos which are compatible with both xvid and divx. Also disable "film effect" in the "playback" tab when decoding videos for editing. What it does is adding noise, which the subsequent encoding will waste bandwidth on.

black borders on the sides

Have you ever noticed black borders on the sides of videos? example:

screenshot of video with borders

If the video is edited correctly, you shouldn't have them here. How they get there: There are various common resolutions to store videos. 4:3 square pixel resolutions such as 320x240, 640x480, etc, are like you'd expect, exactly the "4:3 frame" - it is to show on a TV, or in a player, as a whole, with an aspect ratio of 4:3. Have you ever wondered why VCD video is 352 pixels wide, and DVD video is 720 pixels wide, slightly more than twice the VCD resolution? And why you sometimes see 704 pixels wide video? It is because if a video is 720 pixels wide, the 4:3 frame is only 704 pixels (exactly twice VCD), and it has 8 pixels of padding on the left and right of the scanline, which usually shows as black borders. Below is a DVD frame at native resolution. In an image editor you can measure the width of the picture and the borders.

legal notice: this frame is from a michael palin dvd, i don't own the rights to it. i will remove it on request from the copyright holder, but i think a single frame for discussion purposes is fair use

For PAL, the widths, and editing procedures, are conveniently exactly the same as for NTSC, but the height of DVD video is 576 pixels. Note that a real/analog NTSC frame is 712x486, but everyone conveniently ignores that and uses 704x480 as the 4:3 frame for digital video.

What is the correct way to convert 720 pixels wide video to a resolution such as 640x480, or 320x240, or 352x240? First crop from the left and right until the width is 704. Usually crop 8 from both sides, but the borders may be asymmetric. Then resample/resize to your desired output size.

What is the correct way to convert 352x240, 320x240, 640x480, etc, video to 720 pixels wide for, for example, creating a video DVD? First resize to 704x480, then add borders to make it 720x480.

For 16:9 (anamorphic widescreen), the same applies: the 16:9 frame is 704 pixels wide, the rest is borders.

I'm not going into the problem of interlacing here, it is explained on another site:


Someone invented the 720x540 resolution for videos, with the following seemingly good arguments: Why this is wrong: as explained above, the 4:3 frame of PAL and NTSC video is not 720 pixels wide, it is only 704 pixels. So a correct resize from 720x540, to PAL or NTSC, means resizing to 704x480 (or 704x576), then adding borders, so you are resampling on both axes anyway, defeating reason #2. This resolution should have been chosen as 704x528, then both requirements would have been satisfied.

I once encountered this horrible video editing botch job from p2p, a video of alizee - j'en ai marre, live, by M16 (is M16 the one who edited this?)

screenshot from video

the TV studio sent the first few seconds as interlaced video (720x576 PAL), then switched to progressive, by discarding fields (288 effective scanlines, the other scanlines are linearly interpolated) Which operations have been done on this:

The resulting video shows resizing artefacts on the many diagonal lines in the video, and violates the rule of maintaining the horizontal resolution (13.5 MHz). For the challenge, to see if i could do it, i wrote an algorithm to get back the original half height PAL frames (704x288). This means undoing the pixel resizing, interpolating back the missing scanlines, and padding. I was successful; the result:

screenshot from video

Note how the picture is sharp and all diagonal lines look correct. While the aspect ratio is obviously wrong here (this is normal for video material), a player could correctly show it as 4:3.


the TV industry defined two rectangles in the 4:3 frame - a text safe rectangle within which text (subtitles) should be, and an action safe rectangle within which anything significant should happen, to be 0.8 and 0.9 times the size of the frame. The purpose is to deal with overscan on TV's. One can consider the text safe rectangle to be a bit small (too big borders) to look good on a PC, but i'd definitely keep all added subs, texts, etc, within the action safe rectangle, which i think is safe with most TV's made in the last 15 years

text and action rectangles

The text and action safe rectangle. Note how the subs and karaoke, added by the fansub group, stay within the action safe rectangle here.

text and action rectangles

a subtitle added by the original creators of the anime, exactly within the text safe rectangle.

TV commercial - subtitlesTV commercial - text

This is from a commercial video which has been on TV. The subtitles are outside the text safe rectangle, but well within the action safe rectangle. Everything in the second screen is exactly within the text safe rectangle.

dream hunter REM, fansubs

Fansubs, falling within the action safe rectangle.

Given the definition, and some good examples, the problem: most fansub groups don't care about this, and make their subs almost touch the bottom of the screen, using as argument "We don't want to watch it on a TV, or we adjust our TV's. So you should do the same". Some screenshots follow:

animeone, fansubsno-subs, fansubs

Fansubs by AonE (hard subs), falling well outside the action safe rectangle. Notice how the scrolling text i got in there by coincidence is exactly within the text safe reactangle. Fansubs by "No subs" (soft subs), falling well outside the action safe rectangle.

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