ffmpeg commands

Check file info:

- ffmpeg -i <input>

- ffprobe <input>

Output file:

ffmpeg -i <input> -filter:v fps=fps=30 <output>

ffmpeg -i <input> -filter:v fps=fps=30 -b:v 20080k -b:a 201k <output>

ffmpeg -i <input> -filter:v fps=fps=30 -b:v 10040k -b:a 201k <output>

ffmpeg -i 20210113_2_24fps.mp4 -filter:v fps=fps=30 -b:v 20080k -b:a 201k 20210113_3_30fps_2.mp4

ffmpeg -i 20210113_2_bg1.mp4 -filter:v fps=fps=30 -b:v 10040k -b:a 201k 20210113_2_bg1_30fps_tbr10M.mp4

ffmpeg -i love.mp4 -filter:v fps=fps=30 -b:v 20M -b:a 127k love_30fps_tbr20M.mp4

Video Recording from screen

I posted an article on video editing before. This one is about recording video from computer screen with sound.

The Software

The software used is freeware Camstudio from camstudio.org.  It captures both motion picture from selected screen area and sound.

Capture Audio

Even if you put on headphone, the sound can be captured.

File Size

The resulted avi file may be huge, e.g., about 1.6GB for 2.5 minutes. That's about 10MB/second. To shrink the size, it also contains a SWF producer to convert AVI to SWF format. Another option is to use VideoPad video editor, which can convert the avi file to a much smaller avi file (HD 1080) of about 90MB, or about 0.5MB/second. That's 20 times reduction in size. Quality does not degrade noticeably.

Recommended Settings

- Options -> Video Options, set Quality to 100, Framerates to 50 frames/second (use slider at bottom).
- Options -> check "Record Audio From Microphone"
- Options -> Program Options -> Name of AVI file (Automatic file naming)


Possible Problems

- Sometimes if audio is not recorded, you may need some configuration to use the Stereo Mix option. See: Audio: record from Microphone.

- Error message: "File Creation Error. Unable to rename/copy audio file". This happens when the AVI video is long and video size exceeds 2GB, which is the size limit of a AVI file. The solution is to decrease recording frame rate, e.g., from default 200frames/second to about 25 frames/second. See here.

Video Editing

I'm making videos recently.

I use Sony DSC-T90 to shoot HDTV-720p quality video. The format is MP4, which can be played by VLC media player.

Next I use VideoPad Video Editor to edit it. Different clips are cut and put together. It seems like the subtitle added is not in nice font. It looks rather stout. When saving movie the YouTube HQ format (.flv, 854x480, 25.00 standard frame rate) so far gives the best quality. I tried other formats such as HD1080, HD720, Widescreen TV and Traditional TV, and used other file format (primarily .wmv), all give aliased graphical effect. .flv format can be played by VLC media player. However there is no way to drag on the progress bar, once you do the VLC media player ends the play. Also the VLC media player needs download and install for most windows users and not so convenient.

So I use the Prism Video File Converter Plus to convert from .flv format to .wmv format. This has much better quality than the .wmv file directly generated by VideoPad Video Editor. I'm hoping to add subtitles using Windows Movie Maker now.

Well, Windows Movie Maker does not keep the widescreen setting of the movie. So I'm now trying Subtitle Workshop. It's said the version 2.51 is the best, latter versions not as good. So I downloaded Subtitle Workshop version 2.51.

- 10/19/2010
Subtitle workshop 2.51 works great.

VideoPad Video Editor can directly save the movie to .avi format (parameters: custom, 1024x576). This has the best quality, even better than the previous .wmv format converted by Prism.

Font: when saving as .avi, font height 26 looks the best. When saving as .wmv converted by Prism, font height 24 looks the best. Previously I mentioned the font looks stout. That was because the font's border color is white. Set it to black then it's perfect.

- 12/3/2011
Extracting audio from video.

Extracting audio from video can be done using the recent version of VLC media player (version 1.1.11). But when the video is big, VLC will crash. The workaround is to extract the audio from the original video and compile it into a small video file, for example, a video with a still image.

This latter task can be done in two steps: 1) Open the video in VideoPad, split the audio track from video track, choose the audio section needed, open a still image and compile the chosen audio track with the image, save to a new video file (e.g., in wmv format). 2) In VLC media player, open "Media -> Convert/Save", follow the instructions, the audio can be saved into OGG, mp3, mp4, flac, CD formats.