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

I recently needed to post a screencast (before I found this) and ended up using the H.264 codec.
ffmpeg -i \screen-casts\cast-005.avi -vcodec libx264 -acodec libfaac -vb 700000 -f flv out5.f4v

It makes a file that is considerably smaller than using flashsv (I have video in my screen cast) and while the quality isn’t of a lossless standard, it’s pretty darn good. And with it being a .f4v file, it can still do progressive streaming in flash (unlike a mp4 in flash)

cheers
tom

Адобе премахна Lossless кодека след Флаш 7. Точно защото едно нещо в Lossless FLV е винаги няколко пъти по-голямо от същото нещо в Lossless SWF и става безмислица. Wink е идеалната безплатна програма за захват на екрана в SWF.

Стримването пък по идея се прави с постоянен битрейт. А по природа Lossless кодеците имат силно променлив и напълно непредсказуем битрейт. 90% от размера на файла може да е съсредоточен на 10% от продължителността му. И тогава как ще се впише в ширината на канала който му е отреден?

А за програмата – добра е, но при тази цена за съжаление и на мен не ми влиза в работа. Е освен за “лично ползване”, ако така може да се нарече.

Идеята която имах е, че въпросът със захвата на екрана е решен – програмите за отдалечена администрация. Ниско натоварване на системата чрез използване на специален видео драйвер и ниско потребление на мрежа чрез ефективна компресия. BB FlashBack използва тези принципи, нищо повече. И при наличие на програми за отдалечена администрация с отворен код не знам автора на CamStudio из кои облаци лети.

А колкото до ефективното програмиране виж това:
vTute Recorder
http://www.vtute.com/create/
Програмката е 53 Килобайта, не се инсталира, захваща екрана и експортирав Lossless FLV. Почти идеална работа, като изключим, че натоварва умерено при захват и слага воден знак. И няколко допълнителни опции не биха били излишни. Т.е. не е толкова сложно човек да реши въпросите си и сам, но както винаги времето никога не стига.

1.MSU Screen Capture Lossless Codec съм го пробвал, но за нищо не ти помага, защото не може да се използва във flv, т.е transcode-ваш пак. Все пак е добър междинен формат за пестене на място
2. SWF също не грее – трябва си FLV, за да се stream-ва.
3. Програмата, която посочваш може да е добра, но за толва пари не ми върши работа