Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Image vs. sound quality in videos and audio lectures?

  1. Jul 6, 2010 #1
    I have been going through some great science lectures I have downloaded from itunes U from Apples itunes store. You don't have to own an ipod to use them as they can be viewed for free on a computer.

    Unfortunately the sound quality on many audio and video lectures is very poor. We can take videos of great quality with inexpensive cameras but quality sound capture seems to require a lot of work. Why don't we have inexpensive devices which record quality audio, or do we?

    What suggestions might you give to some science department that might want to record their lectures in good quality sound? Is good sound capture hard to do?

    Thanks for any help!
  2. jcsd
  3. Jul 7, 2010 #2


    User Avatar
    Science Advisor

    But is the problem actually one of poor "sound capture" or is the problem due to the subsequent audio compression? Can you tell me what is the bitrate and codec of the audio stream in the offending videos?
  4. Jul 7, 2010 #3
    I would hazard a guess that most video sound is recorded using a microphone that is built-in to the camera, and probably not very directional. Usually the camera is placed at the back of the room where the mic will pickup every little cough and fart that the audience is capable of producing, along with all the "room tone" reverberation and wonkyness.

    The first fix would be to put an external directional microphone on the ceiling someplace near to and pointing at the speaker (on the ceiling so folks don't trip over it or stand in front of it). A better fix would be a wireless lapel mic clipped to the speaker, but that also gets whacked and rubbed occasionally.

    What's so amazing is that our ears are so good at picking signal out of noise to start with. You don't notice it until you get some bad sound like you describe that is missing all the binaural and physical cues that help us do the cocktail-party extraction.

    Sound recording should be left to the professionals....heh.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook