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The Difference between AC3, PCM and MP2, the Most Common Audio Formats of DVD


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Audio is a very common part in DVD, simultaneously, audio formats are very complicated, there are lost of audio format intended for DVD, and it’s not that easy to figure out the difference between each other.

Not just audio format problem, perhaps many of us have lots of questions about video formats, like how to convert DVD movies to other formats, actually, this is much easier than what we are going to talk about, for example, how to convert DVD to AVI? If you are using Mac OS, what you need is a dvd to avi ripper for mac, what I’m saying is you can convert DVD to any other format you want with a third-party tool. So it won’t be hard to understand that, now let’s back to audio thing.

Each audio format intended for DVD has different compression ratio and quality. There are three main types of audio: AC3 (Dolby Digital), PCM (uncompressed), and MP2 (MPEG Layer II). The most common quality of audio in DVD is 48hz (frequency), with Dolby Digital 5.1 (surround sound).

AC-3 (short for Arc Consistency Algorithm #3) is a type of Dolby Digital audio format. And the Dolby Digital is the common version containing up to six discrete channels of sound. The most elaborate mode in common usage involves five channels for normal-range speakers(20 – 20,000 Hz) (right front, center, left front, right, left surround)and one channel (20 Hz – 120 Hz allotted audio) for the subwoofer driven low-frequency effects. Mono and stereo modes are also supported. AC-3 supports audio sample-rates up to 48 kHz.

PCM is basically the carrier format used in CD audio and most other uncompressed digital audio formats. There are several varieties of PCM and they vary based on the bit depth and sampling rate. CD audio uses a 16-bit word length and a 44.1 kHz sampling rate. PCM is a sound format prior to DVD-A and SCAD. There are a few demo disk (The Ultimate DVD Series) out there that have music tracks with this format its sound good, a bit above normal CD’s. Most newer or highend receivers will auto select over to 96khz or 48khz sound processing when playing a disk. It’s only a stereo format. Common bitrate is 1536k.

Another form of MPEG audio is MP2. This format is not officially supported for NTSC video. If you have MP2 audio then do not recompress it to AC3, recompression may destroy the quality. So, leave it untouched. But if you have PCM uncompressed source, I definitely recommend you guys to use AC3 instead of MP2. Common bitrate is 256Kbit/s. The main advantage of MP2 is good compression level and ease of audio conversion from SVCD or VCD. The main disadvantage of MP2 is not very good quality, and lack of support by all devices.

You can transfer videos and audios from DVD to almost every other platform, like the hot iCloud, you can share whatever you want with others via iCloud, I guess everyone know how to operate iCloud like how to delete apps from icloud. Anyway, as long as you have a clear understanding about all kinds of formats, then you won’t feel restricted when you utilize them.

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jessiemroz Article's Source: http://articles.org/the-difference-between-ac3-pcm-and-mp2-the-most-common-audio-formats-of-dvd/
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  • Posted On December 16, 2011
  • Published articles 10

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