FFmpeg and quality of the output video

[Vidameker]

Hi all,

I need to convert a BMP file to a video (mpeg2 or mpeg4) but the quality of the output video is not as good as i want.

I tried both commands :
ffmpeg -loop_input -i sortie001.bmp -r 25 -qscale 1 -an -t 10 -b 5000000 -vcodec mpeg4 video.mp4
and
ffmpeg -loop_input -i sortie001.bmp -r 25 -qscale 1 -an -t 10 -vcodec mpeg4 video.mp4


The BMP source file properties : 720x576, 24bits, 96dpi
Here are two screen captures of parts of the images to show you the differences :

bmpsource.bmp : a sample region of the BMP source
VLCscreencapture.bmp : a sample region of the output video (screen capture made by VLC)

As you can see the output video image is slobbering.

What to do for the video to be very clear?
(I can change the BMP source if necessary).

Regards,

[Soopafresh]

Are you positive the source dimensions are exactly 720x576 ? The dimensions should be divisible by 8 for good results

I get the best results by doing the conversion in 2 steps - 1) HQ MJPEG AVI --> 2)HQ h264 MP4

ffmpeg -loop_input -vframes 300 -vcodec mjpeg -qscale 1 -y -i input.jpg output.avi

ffmpeg -i output.avi -vcodec libx264 -b 3000k -g 3 -bf 3 -b_strategy 1 -coder 1 -qmin 10 -qmax 51 -sc_threshold 40 -flags +loop -cmp +chroma -me_range 16 -me_method hex -subq 5 -i_qfactor 0.71 -qcomp 0.6 -qdiff 4 -directpred 1 -flags2 +fastpskip -dts_delta_threshold 1 -an -y  output.mp4

Download enclosed zip file and test it out yourself.

[jagabo]

Colors are encoded at half resolution in MPEG files. So small colored text on a colored background will get blurry. Add some black text on a white background, or vice versa, and compare.

Here's some similarly sized and colored text on on a similar green background, and the same text in black on a white background (left), and what they look like after conversion to the YV12 colorspace where the colors are encoded at half resolution (compared to the grayscale image):