what makes it good or bad?
The "quality" depends on several factors:
- Resolution. 640x480 is ideal for US TV, and 4:3 DVD rips.
Note that both lower and higher resolutions can decrease
the overall quality. The resolution should ideally be the same as
what the original source used... never higher, and preferably not lower.
However, for higher-quality sources like HDTV, bigger resolutions are good.
- Codec. XviD is preferred, and DivX5 is good too. Points are lost
if the files use lower-quality codecs (mpeg1/2 for (S)VCD), or proprietary
codecs (Windows Media, Real, etc).
- Bitrate. If the bitrate is too low, the video looks crappy. If the
bitrate is too high, the files are too big and take too much CPU to play.
Generally, a half-hour cartoon should be around 175MB or 230MB, and an
hour-long TV show about 350MB. Movies should be 700MB or 1400MB,
depending on their length and content.
- File size. It is useful to make files an appropriate size for copying
onto CD or DVD media. This means that files should be some fraction of
700MiB or of 4.7GiB. Useful sizes include: 175MiB, 230MiB, 350Mib, and
700MiB for CDs.
- Container format. OGM or MKV is preferred, and AVI is acceptable.
I avoid MOV and RM, and there's not much point using regular MPEG unless
you're making (S)VCDs. (if you want (S)VCDs, transcode them yourself)
- Intactness. Corrupt files are bad. So are videos with annoying logos
stuck onto them. Skip the "3nc0d3d by M3!" inserts and overlays, please.
If it's that important to let people know who you are, add a subtitle
track with your info in it. Other errors can cost points too, such as
incorrect aspect ratio, extra blank space around the image, badly
translated subtitles, interlacing, inconsistent file sizes, etc.
- Number and type of tracks. One video track with one audio track is
okay, but extras are good. I like having multiple audio tracks to
choose from, and multiple subtitle languages.
The vague ratings I give are as follows:
- RAW: Uncompressed; no quality loss at all.
- VHQ: About as high quality as you can get. Probably has extra features, too.
- HQ: Small visible artifacts, but no real problems.
- MQ: Noticable artifacts or problems, but not annoying to most viewers.
- LQ: Low enough quality that even regular viewers will dislike it.
- VLQ: So bad it's almost unwatchable.
- ICK: Complete rubbish. May be useful for generating random numbers, but not much else.
Some things to note:
- Bigger files are not necessarily higher quality. I'll take a
350MiB XviD video over a 700MiB SVCD version of the same show, any day.
XviD (mpeg4) compresses so much better than SVCD (mpeg2) that it can be
half as big and still be higher quality. Especially if the original video
source was HDTV or otherwise higher quality than either video.
Using SVCD for a TV show is kind of like compressing a music CD (~1400kbps)
using a 22khz 16-bit mono WAV file (~350kbps) instead of using the much
higher quality ogg vorbis codec (~175kbps). The wav file will be only 1/4
the size of the CD, which is good, but it won't sound very good. However,
you could use ogg vorbis to make it half the size of the wav, and the result
would be nearly identical to the original CD audio. For an hour-long album,
you end up with either 150MiB of low-quality wav audio, or 75MiB of
high-quality vorbis audio. Why waste more space for less value?
- Higher quality doesn't always mean more value. I avoid some
types of files simply because they are of no value to me. For example,
the Apple music store sells high-quality music but the files have DRM
restrictions built in to keep anyone from doing useful things with the
music. The audio quality of those files is really quite high, but that
is irrelevant if I can't do what I like with the files.