Recording screen via Quick Time Player along with the sound As seen from some of the youtube videos I tried to record a video playing on my mac but I couldn't hear anything. I chose File -> New Screen Recording in Quick Time Player. Any other software to do it or any other suggestions for how I can do it?

Thanks
QuickTime alone won't capture computer audio along with a screen capture, but combined with a free utility Soundflower, you can do this.

MacWorld has a step-by-step guide, but the basic idea is to install Soundflower and set your computer audio out to Soundflower, so system sounds play to it and not to the speakers. Then in QuickTime, when you set up a new screen capture, select Soundflower as the audio source. Then you can do a screen recording and capture system audio at the same time.

Note that this is the free but messy version. Software like Screenflow does this sort of thing very well, but costs $99.