If you just want to download and convert YouTube .flv files on Mac OS X, here this FLV Converter for Mac is your best choice.
FLV/F4V Converter for Mac is developed for converting FLV and F4V files to your required file types, including MOV, MPG, VOB, MKV, TS, AVI, MP4, etc. More than converting FLV and F4V files to other formats, it also features "Merge into one file" to combine multiple video clips into a single file.
A Mac FLV Converter, F4V Converter, and MP4 Conveter
The FLV Converter for Mac deals with more than FLV video clips, it's also a F4V Converter and MP4 Converter that can convert and edit H.264/ MPEG-4 AVC encoded F4V and MP4 files downloaded from YouTube, Netflix, and more web videos.
Convert FLV, F4V, MP4 at a faster conversion speed
The FLV Converter for Mac is much tested and proved to be faster than overwhelming majority Mac FLV Converters on market. Try it out and you'll learn how fast it is.
Perfect Audio and video sync ability and bulit-in codec
The FLV Converter for Mac adopted advanced audio and video sync technology that free you from the out of sync troubles. The program uses built-in codec and will not install any codec on your computer, so there's no concern about unexpected codec problem.
Optimize Flash videos for iTunes, iPad, iPod, iPhone, etc
With this FLV Converter for Mac, Flash videos and MP4 files downloaded from video hosting site can be easily turned into MPEG-4 and H.264 encoded MOV, M4V, MP4 of 1280*720 (Apple TV 720p, iPad HD, iPhone 4 HD, iPod Touch 4th Gen HD), 720*480 (DVD standard), 640*480, 480*320, 320*240 (earlier iPod Nano, iPhone 3G, iPod Touch) .
Customization options like Trim, Crop, Merge, Replace audio
The program's editor section allows you to get any video length you want with Trim; cut off the black edges and unwanted video area easily with Crop; merge many videos into a signal one; replace the original audio even adjust audio volume.
Different watermark types
This program supports to add different watermark types, including text, image (including GIF), and video watermark to the MOD. With its video watermark functions, you can add a picture-to-picture effect to your video.
Special video effects
If you like, you can adjust the video brightness, contrast, saturation, or add special effects like simple laplacian sharpen, gray, flip color, invert, aged film to have a fun. Meanwhile, you can check deinterlacing to get better video quality.
Capture the snapshot images
You can capture the snapshots images as your wallpaper or editing elements if you like.