ffmpeg.exe -i %1 -r 1 xxx-%06d.JPG what is better quality capture command?

[sommers]

1. ffmpeg.exe -i %1 -r 1 xxx-%06d.JPG
2. ffmpeg.exe -i %1 -r 2 xxx-%06d.JPG
3. ffmpeg.exe -i %1 xxx-%06d.JPG

1.'s jpg quality is less than poor, 720 DVD image becomes 45k JPG
2.'s jpg quality is retared , 720 DVD image becomes 18k JPG
3.'s jpg quality is unacceptible , 720 DVD image becomes 13k JPG

why does the JPG quality depend on the time? this doesnt make sense to me.
what is the command that i can improve the JPG quality?

A command for JPG quality 80% ?
B command for JPG quality 85% ?
C command for JPG quality 90% ?

[sneaker]

Default is probably a bitrate (bits per time) so if you change fps (frames per time/second) you change size of each picture.

Try instead -q:v from 2 (best) to 31 (worst).

[sommers]

1. ffmpeg.exe -i %1 -r 1 -q:v 2 xxx-%06d.JPG makes 50k JPG from 720 DVD image
2. ffmpeg.exe -i %1 -r 2 -q:v 2 xxx-%06d.JPG makes 50k JPG from 720 DVD image

1. and 2. are time independant, the JPG quality is kind of good enough, but not totally keepable.

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3. ffmpeg.exe -i %1 -r 1 -q:v 31 xxx-%06d.JPG makes 12k JPG from 720 DVD image
4. ffmpeg.exe -i %1 -r 2 -q:v 31 xxx-%06d.JPG makes 12k JPG from 720 DVD image

3. and 4 are time independant


question 1 : where can I find this kind of options "-q:v from 2 (best) to 31 (worst)"? because i couldnt find it anywhere in the document.
question 2: are there any reasons to use "-q:v" thing in BMP output like ffmpeg.exe -i %1 -q:v 31 xxx-%06d.BMP? because BMP is not lossy.
question 3: -q:v 1 also works but the result is the same as -q:v 2

[sneaker]

1. https://ffmpeg.org/ffmpeg.html#Main-options (+ Google, official ffmpeg documentation is often lacking. Worst case you have to look into the source code.)
2. That should not be the case. (But I don't know complete ffmpeg project.)
3. I assume values are clamped, i.e. any value smaller 2 is set to 2 and any value greater than 31 is set to 31.

[VideoGuruDude]

There is some good google search data on this subject, and I do think Ive seen where the lower the number can go is 2 or 3 on the quality scale (for JPEG image output).
I have it setup on my work computer to convert video to JPG, but the data is in google...

HTH,
Andrew