Some General Questions

[axxo]

Q.1. Which audio format is the best in terms of quality? MP3, AC3, MPEG Audio, LPCM Audio, AAC Audio or something else?

Q.2. Which audio format is most efficient in terms of size?

Q.3. Why VCD's have MPEG Audio at 44100Hz while DVDs have AC3 Audio at 48000Hz? Why the difference of 44100 n 48000 Hz?

Q.4. Audio CD's have Audio at 44100 Hz, while DVDs have Audio at 48000 Hz, why? Does it makes any clearity?

Q.5. Human ear can hear frequencies higher than 20000Hz, then how we manage to hear these higher frequencies?

Q.6. Is AVI (Xvid or Divx) better than VOB (MPEG-2) format found in DVDs? If yes, how? If not, why not?

Q.7. I generally encode DVDs to AVI format to save space, and usually I found that AVI files at bitrates upto 2500 kbps offer almost the same quality as DVDs at bitrates of 7000-8500 kbps, is it true? If yes, then doesn't the MPEG-2 involves wastage of space and shouldn't it be done away with AVI format in DVDs?

Q.8. Which Video format is best in terms of size and quality? (MPEG-4 codec I guess..)
?
Q.9. Does these frequencies (used in Audio format) of 48000Hz, 44100 Hz etc take any space while we encode them?

Q.10. For AVI files, how are Video Size and Video Bitrate related to the quality of the video file? Please explain this question in detail.


thanks in advance...

[froggy1]

Q1 - there's no such thing as best, even for audio. Though in terms of compression -> quality, AAC is pretty good
Q2 - AAC (more precisely HE-AACv1 (v2 is horrible)) and Vorbis
Q3 - 44100 Hz requires lesser bitrate than 48000 Hz and thus one can squeeze more on a VCD
Q4 - More samples -> smoother
Q5 - use search
Q6 - That depends on a lot of things and you can't say this or that is better
Q7 - Again depends on content and settings used to encode
Q8 - no such thing as best, per forum rules and also reality
Q9 - read up
Q10 - More bitrate -> higher quality -> higher filesize (though not always as it depends on input content and other settings used to encode, including codec)

Also, read the forum rules!

[CWR03]

You've asked at least one of these questions before, about audio quality, and you received some very good answers. Most of the rest of your questions can only be answered by you, for example I can quite easily tell the difference between an encoded AVI and the original DVD. If you can't, choose the one that best suits your needs and your perceptions. You should also take froggy1's advice and re-read the forum rules (http://forum.doom9.org/forum-rules.htm) to which you agreed when you signed up to this forum, particularly 1, 1a and 12.

[yetanotherid]

Most of the rest of your questions can only be answered by you, for example I can quite easily tell the difference between an encoded AVI and the original DVD.

Are you saying you can pick them when played side by side, or are you saying that if you walked into the room and a video was playing full screen you would know if it was the original DVD or an AVI?

[yetanotherid]

Q.2. Which audio format is most efficient in terms of size?

If you're using AutoGK it doesn't matter. AutoGK can only use the original audio or create an MP3 from it. AC3 audio in a DVD is generally at a bitrate of 192kbps or higher. Unless you're going to convert that audio to an MP3 using a lower bitrate than the original AC3 you might as well use the original, as you won't save yourself any space. MP3 is only stereo. AC3 can do surround sound.


Q.4. Audio CD's have Audio at 44100 Hz, while DVDs have Audio at 48000 Hz, why? Does it makes any clearity?
Q.5. Human ear can hear frequencies higher than 20000Hz, then how we manage to hear these higher frequencies?

We don't hear them. 44100Hz is the sampling rate used. The sample rate needs to be slightly higher than double the highest frequency being sampled.
48000Hz is used, I believe, as some audiophiles claimed that 44100Hz wasn't quite a high enough sampling frequency.


Q.7. I generally encode DVDs to AVI format to save space, and usually I found that AVI files at bitrates upto 2500 kbps offer almost the same quality as DVDs at bitrates of 7000-8500 kbps, is it true? If yes, then doesn't the MPEG-2 involves wastage of space and shouldn't it be done away with AVI format in DVDs?

It's more a case of DVDs themselves which are being done away with and replaced by Blu-ray. It's not really practical to change the type of video used on a DVD as the majority of DVD players wouldn't be able to play it.


Q.9. Does these frequencies (used in Audio format) of 48000Hz, 44100 Hz etc take any space while we encode them?

Yes. If you're really keen you can convert 48000Hz audio to 44100Hz audio and it'll give you a slightly smaller file size. I can't hear the difference.


Q.10. For AVI files, how are Video Size and Video Bitrate related to the quality of the video file? Please explain this question in detail.

The higher the bitrate, the better the quality and the larger the file size.... generally speaking.