It helps to remember that a video stream is a series of still images.
If you are using an image editor to resize an original, you want your original to be much larger than your current need.
If you want all of your photos, for instance, to be more “compatible” with putting onto a DVD — thus always fitting within the 854×480 box, and usually only being 854×480 and 640×480 (16:9 and 4:3) because those are also the two modes that a DVD has (widescreen or fullscreen). (The DVD will never use square pixels for you.) … If you want those conditions, you would want to start with something that your computer can not only handle, but handle at a comfortable speed. If your display is 1920×1080, it would be good to use something no more than two or three times that size, that you then cut to fit the 16:9 box, and then resize to 854×480 — or cut to fit the 4:3 box, and then resize to 640×480.
Videos use the same principle. It’s common now to use 2160p. Whether or not your own computer has enough CPU power and enough RAM, and whether or not your own video editor can handle something that size, tends to determine if you end up using it. (If your computer could, you should. It’s much, much faster to put less strain on the CPU and RAM, but you’ll probably have the resulting 480p MP4 for such a long time that you’ll always be grateful when you watch it that you didn’t rush the process.)
The 16:9 box for 480p is 854×480. An MKV with the dimensions 1920×800 (2.40:1) will fit that box with the dimensions 854×356 (using a modulus of 2).
If you have, say, an MKV with dimensions 1920×796, it’s not meant to be that way. It’s due to one of two things. Two pixels were accidentally cropped out of the original, and they’re retaining the aspect ratio by retaining that error; or the wrong modulus was used, and it’s now technically in the wrong aspect ratio.
Either way, when resizing to a 480p MP4 (probably in Handbrake) pretend you’re dealing with the usual dimensions. (In this case, assuming 1920×800 to convert to 854×356.) (Something that will force you to untick the Keep Aspect Ratio box. — You’re actually fixing the aspect ratio, so no worries.) The error itself will not be visually discernible.
The image you use should be a high quality JPG or PNG at either 3840×2160, 2560×1440, 1920×1080, 1280×720, 854×480, 640×360, or 426×240.
I know that audio will be 192 kb/s at 1080 and 720, and drop to 64 kb/s beneath that. I don’t know if higher resolutions result in better bitrates.
Use a standard audio bitrate above 192 kb/s (if that’s what you’re aiming for). I suggest 384 kb/s. With every encode you should start with something larger than the result.
As far as I know, the only program that allows you to use a single image for the video stream is TMPGEnc. You can also use a program like Vegas or Premiere to create and merge audio and video streams.
Programs that I know won’t help are Handbrake, XMedia Recode, Avidemux, and Freemake, because they only accept videos as video input.
Picture tab settings
I always tick Web Optimized. That makes the video streamable. I don’t need to stream it, but then I’m a bit of a survivalist collector, so I like to have videos with maximum usefulness. I don’t tick that box anymore, because that might just have been dumb of me.
- The first thing on the picture tab is to make sure there is no cropping (i.e. 0 on all sides). Put it on Custom and remove any cropping. I don’t know why it sometimes adds cropping, but it’s always wrong. The big exception is that sometimes a movie in, say, 1920×800, will actually be 1920×1080, with black bars on the top and bottom hard-coded in. Then let it crop that out.
- Make sure Modulus is set to 2. Set Anamorphic to none. Then resize your height to 480 unless that would cause the width to be greater than 854 — in which case set the width to 854, thus automatically resizing the height to something less than 480. (It’s automatic because Keep Aspect Ratio is ticked.)
Filter tab settings
- Make sure all filters are turned off. These are really for DVDs anyway. Don’t use a filter unless you know what you’re doing.
Video tab settings
- Keep the Video Codec as H.264 (x264). Use a constant framerate (not a variable framerate). Set the Framerate to Same as source. The only exception to this is if you have a video (usually a sports video) with a doubled framerate (i.e. 60 fps for NTSC countries and 50 fps for PAL countries, even though we’re not dealing with DVDs.) Then change 60 to 29.97, or 50 to 25. You would have to look the fps up ahead of time, such as with MediaInfo.
- I set the Quality to Avg Bitrate at 2000 kbps. (I find 2000 is a good balance between size and quality.) I tick 2-Pass Encoding and Turbo first pass. These are my own preferences, but I think they’re good ones for anyone to use.
- I use an encoder preset of Veryfast. It’s about how fast your CPU is. I have an old computer, so my patience can’t take a slower encode speed. A slower speeds yields greater quality.
- I set Encoder Tune to none. That’s just a preference. I tick Fast Decode, to make the video more useful, though it may not be required.
- I set the Encoder Profile to High. That’s a quality thing. I don’t know the specifics of Encoder Level, so I consider it wise to always set that to Auto.
Audio tab settings
- I change the bitrate to 256. That’s just a preference. I change the Mixdown to Stereo, if it already isn’t set that way. I also make sure the Samplerate is 48, as almost anything video is going to have a 48 kHz samplerate. (Because of that, leaving it at Auto is probably fine. It’ll probably give you 48 anyway. I’m just a stickler.)
It’s okay to leave the Subtitles and Chapters tabs alone.
1080, 720, and 480 refer to the height of the video. But if you have, say, an MKV that is 1920×800 (2.40:1) then that MKV is considered a 1080. The reason the height of 800 puts this in the same category as a video with dimensions of 1920×1080 is that they both fit into the same box. The box for 1080p is 1920×1080. So when resizing you are always fitting videos into the 16:9 boxes of 1920×1080, 1280×720, or 854×480.
If you’re converting from 1920×800 to a 480p video, it would be incorrect to change the dimensions to 1152×480, as that exceeds the 16:9 box of 854×480. The correct dimension is 854×356. If you’re converting to 720p, then it would be incorrect to change to 1728×720. The correct dimension is 1280×534.
The term “aspect ratio” with DVDs is usually applied to the ratio of width to height of the video. Such as 4:3 or 16:9. But there is also the pixel aspect ratio. YouTube, for instance, will only accept videos with a 1:1 PAR, i.e. “square pixels”. Everything Blu-ray has square pixels. DVDs, however, do not.
DVDs are 720 pixels wide by 480 pixels tall, but depending on its two modes, the width is either shrunk or expanded. (This is for NTSC encoding, as opposed to PAL.) Depending on whether the video is 16:9 or 4:3, in square pixels the real width and height is either 854×480 or 640×480.
So NTSC is North America and Japan and a few other places. It’s just a kind of encoding of the original video. PAL is different regions of the world. A PAL DVD will be 720×576, and its pixels will be shrunk width-wise beyond both 4:3 and 16:9. If it’s set as widescreen (16:9), then to get square pixels you would change the width to 1024×576. If it’s fullscreen (4:3) you would change the width to 768×576.