Focus question

[zsuppguy]

Hello ...

I have an avi video which was made based on a slide presentation file. After converted the video to MP4, i realized all slide's text become fuzzy. I still can read the slides but it seems like a blur photoshop filter was applied.

Is there anything with avisynth to improve the focus on this video ?

thanks !!

[filmboss80]

Your post is slightly confusing. Did the blur occur only after the avi was converted to mp4, or were the slides never sharp at all?

It is quite possible that your mp4 conversion settings allocated too little bitrate or had a thumbnail-sized aspect ratio.

But if the slides were originally shot with soft focus, sharpening filters will only do a slight improvement, but reintroduce noise and grain.

[zsuppguy]

hello filmboss80 ... thanks for your reply...

The slides are perfect. The avi file created with the slide are nice too.

The problem happen when i'm converting the avi to mp4.

would be possible provide some examples using these plugins ?

i need to say that this is one time work, and i'm not familiar with video world.

[jagabo]

What frame size was the source? What frame size was the MP4 file? What video codec did you use? Note that most MPEG codecs encode colors at half the resolution of the luma (grayscale) channel. Small colored text will always be blurry compared to grayscale text:

[zsuppguy]

jagabo ... this is exactly what i'm looking for..... but i have no clue how to identify what you are asking for, so i listed all information for the source file.

Could you tell me pls how can i walk in direction of the example you have posted ?
I really appreciate, Thanks !!

General
Complete name                    : C:\Video\test\v1.avi
Format                           : AVI
Format/Info                      : Audio Video Interleave
File size                        : 177 MiB
Duration                         : 44mn 4s
Overall bit rate                 : 562 Kbps
Writing application              : Lavf52.14.0

Video
Format                           : S-Mpeg 4 v2
Codec ID                         : MP42
Codec ID/Info                    : Microsoft MPEG-4 V2
Duration                         : 44mn 4s
Bit rate                         : 453 Kbps
Width                            : 368 pixels
Height                           : 208 pixels
Display aspect ratio             : 16:9
Frame rate                       : 25.000 fps
Bits/(Pixel*Frame)               : 0.237
Stream size                      : 143 MiB (81%)

Audio
ID                               : 1
Format                           : MPEG Audio
Format version                   : Version 1
Format profile                   : Layer 3
Format_Settings_Mode             : Joint stereo
Format_Settings_ModeExtension    : MS Stereo
Codec ID                         : 55
Codec ID/Hint                    : MP3
Duration                         : 44mn 0s
Bit rate mode                    : Constant
Bit rate                         : 96.0 Kbps
Channel(s)                       : 2 channels
Sampling rate                    : 44.1 KHz
Stream size                      : 30.2 MiB (17%)
Alignment                        : Aligned on interleaves
Interleave, duration             : 26 ms (0.65 video frame)
Writing library                  : LAME3.97

[jagabo]

If that is your source small colored text should already be blurry (I'm pretty sure MP42 uses the same 4:2:0 chroma subsampling as other MPEG codecs). What are the properties of your MP4 file? Is it the same 368x208 resolution?

[zsuppguy]

Output file comes out with this conf:

General
Complete name                    : C:\Video\test\ex31.mp4
Format                           : MPEG-4
Format profile                   : Base Media
Codec ID                         : isom
File size                        : 505 MiB
Duration                         : 44mn 4s
Overall bit rate                 : 1 604 Kbps
Movie name                       : ex31
Encoded date                     : UTC 2010-01-12 05:39:21
Tagged date                      : UTC 2010-01-12 05:39:21
Writing application              : Lavf52.31.0

Video
ID                               : 1
Format                           : AVC
Format/Info                      : Advanced Video Codec
Format profile                   : Main@L3.1
Format settings, CABAC           : Yes
Format settings, ReFrames        : 3 frames
Codec ID                         : avc1
Codec ID/Info                    : Advanced Video Coding
Duration                         : 44mn 4s
Bit rate mode                    : Variable
Bit rate                         : 1 522 Kbps
Width                            : 1 280 pixels
Height                           : 720 pixels
Display aspect ratio             : 16:9
Frame rate mode                  : Constant
Frame rate                       : 25.000 fps
Resolution                       : 8 bits
Colorimetry                      : 4:2:0
Scan type                        : Progressive
Bits/(Pixel*Frame)               : 0.066
Stream size                      : 480 MiB (95%)
Encoded date                     : UTC 2010-01-12 05:39:21
Tagged date                      : UTC 2010-01-12 05:39:21

Audio
ID                               : 2
Format                           : AAC
Format/Info                      : Advanced Audio Codec
Format version                   : Version 4
Format profile                   : LC
Format settings, SBR             : No
Codec ID                         : 40
Duration                         : 44mn 4s
Bit rate mode                    : Variable
Bit rate                         : 77.4 Kbps
Channel(s)                       : 2 channels
Channel positions                : L R
Sampling rate                    : 44.1 KHz
Stream size                      : 24.4 MiB (5%)
Encoded date                     : UTC 2010-01-12 05:39:21
Tagged date                      : UTC 2010-01-12 05:39:21

[jagabo]

You can't enlarge the frame from 368x208 to 1280x720 and expect a sharp picture. Here's an example: at the top is some text taken from a 1280x720 frame. In the middle is that same text after the frame was reduced to 368x208 (precise bicubic resizing algorithm). At the bottom is the text from 368x208 frame after enlarging to 1280x720 (precise bicubic again):



See how the small text did not regain all the sharpness of the original? Different resizing algorithms give different amounts of blurriness or blockiness.

[filmboss80]

Bingo. So you're trying to do a blow-up. We did not have that info in the first post. Jagabo's explanation is right on the money. You cannot get high definition out of a low-resolution source. You can only magnify the compression flaws.

[edDV]

Is 368x208 the best you've got? How did it get that small?

Can you go back to the original presentation source slides?