1. Вече от доста време има BB FlashBack Express, която е безплатна.

2. Компресията на Lossless FLV по принцип има 9 или 10 нива. А във ffmpeg опцията flashsv компресира с най-ниското ниво на компресия. Това дава поне 4-5 пъти по-голям файл от най-добрата възможна компресия. Различни пак платени програми могат да компресират с разните възможни нива. Дори намерих един безплатен DirectShow филтър който поддържа всички нива на компресия. Но така и не остана време да го тествам. Там трябваше програма да се пише, не беше обикновен кодек – пусни и инсталирай.

3. H.264 кодека във флаш може да се настрои да дава практически неотличимо от Lossless качество при в пъти по-малък размер. Даже има и Lossless H.264.

http://abaqueiro.blogspot.com/2010/11/screen-capture-in-linux-using-ffmpeg.html

happy screening!!!!

I was more interested in making sure that the WRF to FLV conversion solution I came up with got out there for people to find because that was evil and search results were turning up people saying it wasn’t possible to do the conversion for “free”, which, while false, it does take an insane amount of time.

ffmpeg -i src.avi -acodec libmp3lame -ar 11025 -ab 16000 -ac 1 -f flv -s 466×350 -b 150000 dest.flv

Roughly a 4:3 aspect ratio with a target height of 350 pixels. Videos of all standard sizes seem to work well with these settings (e.g. 1024×768). In a couple instances, the audio was really bad, so I gave that a boost:

ffmpeg -i src.avi -acodec libmp3lame -ar 22050 -ab 32000 -ac 1 -f flv -s 466×350 -b 150000 dest.flv

If I needed to crop the video, ffmpeg wouldn’t let me (cropping errors due to not being in YV12 or something like that), so I had to create an intermediate FLV of the same size and use some ridiculous bitrate to keep ‘q’ low (more on ‘q’ in a bit). After that, I was able to create the final FLV with the borders cropped however I wanted.

In one instance, I had a WebEx .wrf file. To convert that video to Flash, I first installed the hard-to-find, ancient WebEx Recording Editor, loaded the .wrf file into the Editor, and did File -> Export to WMV with the default options. That generated a WMV file that was unfortunately incompatible with ffmpeg. So, I then fired up Windows Movie Maker 2, added the WMV file to the timeline, ‘Finish Movie’ -> ‘Save to my computer’, ‘Show more choices…’, ‘Other settings’, ‘DV-AVI (NTSC)’. This process took a ridiculously long time (several hours) and generated an unnecessarily huge >10GB file. This file was compatible with ffmpeg but I had to use the -r 1 option to force the framerate and the file size to something reasonable (about 60MB). -r is supposedly frames per second (fps) but -r 1 ended up with about 6fps…I don’t know how that works…1 == 6? Regardless, the output FLV was about 300fps without the -r option and several hundred MB, so the savings was huge. Total time to figure all this out for this one video was something like 8 hours. The end result is a slightly blurry video and not the greatest audio. Not bad but not great either when compared to the other video conversions. But way better than nothing at all. Camtasia Studio or CamStudio might have helped shortcut the effort (e.g. cut out the WMV middleman and maybe have a better quality AVI), but that requires equipment I don’t have and didn’t really want to fiddle with. Hopefully these notes will help someone else. To summarize the process to convert WRF to FLV/Flash Video: WRF to WMV to AVI to FLV – with lots of hard drive space, time, patience, and trial-and-error. And next time, don’t record screen video using WebEx’s tools. Ugh.

During all this, I learned that the most important piece of output on the screen from ffmpeg is the value of ‘q’ (‘q’ = quality). If ‘q’ is holding steady at 31, then the quality is going to be terrible and the conversion will need to be run again with different options. A ‘q’ of 2.0 is basically a flawless conversion (very little loss, quite readable). The ‘r’ option is useful if you have a huge number of frames in the source video, which will also affect ‘q’ (I thought about trying fractions of frames for the fps, but didn’t try it to see if it would work). The lower the value of ‘q’, the better the video will look.

Thanks