DVD Discs - The Truth beneath

[sgmane]

The quality of DVD's measured here in india when compared to western countries.

A typical blank DVD disc is 4.7GB. Means when the recording done on the DVD disc for 2 or 4 hrs. (I may be wrong too!)

DVD recorders have 1, 2, 4, and 6 hour record modes and some have 1.5, 3, 8, and even 10 hour modes.

When recording more than 2 hours (means increased in compression of the video format) does it affect the video quality? Typically our indian movies are more than 2 hrs. In that case,the quality of video is poor when compared to western movie dvd recording (because they have max of 2hrs movies and sometimes 3-4 hrs movie)?

The more video time on a DVD disc not only relates to loss of video quality, but also possible decreasing playback compatibility. Due to increased compression it may lead to disc's may be harder to read and may cause skips or freezes on some DVD players.

How do we check to find out that the dvd video quality is good before buying?

 

[rikhav]

The most basic thing you forgot is DVD's also come in dual layer which can hold 8.4 gb

 

[eummagic]

DVDs are available in the following formats:

DVD-5 - 4.7GB i.e. can hold upto 4.37 in computer GB, called as single layer DVD.
DVD-9 - 8.5GB i.e. can hold upto 7.95 in computer GB, called as dual layer DVD.
DVD-10 - 9.4GB i.e. can hold upto 8.75 in computer GB, called as double sided single layer DVD.
DVD-18 - 17GB ie. can hold upto 15.9GB in computer GB, called as double sided dual layer DVD.

Retail DVDs available in India are mostly dual layer (DVD-9 -> 8.5GB) which can easily hold movies 2 hrs plus. DVD-5 & DVD-9 blank media are easily available in India, but DVD-10 & DVD-18 are still yet to come (to my knowledge).

Generally the maximum video bitrate of DVDs are upto 9.8Mbps (both NTSC & PAL). Here Mbps actually means "Million bits per second". If you have noticed playing the DVD in a computer and seeing the video bitrate details, the info shows two things 1) Video bitrate and 2) Variable bitrate.
1) Video bitrate: As said earlier is the maximum bits that the DVD can show i.e. 9.8Mbps
2) Variable bitrate: It is the actual bitrate in which a particular scene of the movie is playing. In other words, this bitrate keep changing according to the video information or scenes in DVD movie. For eg. if the credits are appearing in the DVD movie then the variable bitrate would be in the region of 1 to 2 Mbps since there is not much of video information to display, whereas in action scene or video displaying more colors shows higher bitrate in the region of 8 to 9Mbps.

The average bitrate attained during the movie would be in the region of 5 to 6 Mbps which gives decent picture quality. The more the bitrate, ultimately the file size will be bigger and excellent picture quality.

Additional info:
In Blu-ray, the maximum bitrate is 40Mbps at 1920 x 1080 giving the ultimate viewing experience. But size does matter, to hold the above said movie quality requires 25 to 50 GB depending on the movie playing time.

 

[ajinkya]

"Variable bitrate: It is the actual bitrate in which a particular scene of the movie is playing."

Eumagic,
Is the variable bitrate something that the player (VLC, WMP) decides or is that what is stored on the DVD? As per my understanding, the DVD stores a standard bitrate for each film. So I'm not clear where the variable bitrate comes into play. This can happen only if there is compressed video on the DVD, which the software player (or DVD player) is decoding on the fly. Is this true?

 

[eummagic]

"Variable bitrate: It is the actual bitrate in which a particular scene of the movie is playing."

Eumagic,
Is the variable bitrate something that the player (VLC, WMP) decides or is that what is stored on the DVD? As per my understanding, the DVD stores a standard bitrate for each film. So I'm not clear where the variable bitrate comes into play. This can happen only if there is compressed video on the DVD, which the software player (or DVD player) is decoding on the fly. Is this true?

DVD (720 * 480/576) is a compressed video, but when comparing VCD/SVCD it out performs in accomodating more bitrates. DVD encoded have normally have three parameters 1) Current bitrate, 2) Average Bitrate and 3)Peak bitrate. Though the DVD info shows 9.8Mbps (Peak), during real time playtime depending on the scenes (like action or fast moving sequences) the video bitrate changes. This method of encoding is done to maintain smooth playback of DVD in all DVD players and to avoid buffer underruns. The retail DVDs available in market have a average video bitrate between 4-5Mbps and peak touching in the range of 8-9Mbps.

Certain standalone DVD players (eg. Philips 5986) have the option of displaying video bitrate while the movie is played, shows the real time video bitrate of the movie and it changes according to the scenes.

 

[illusion]

DVD (720 * 480/576) is a compressed video, but when comparing VCD/SVCD it out performs in accomodating more bitrates. DVD encoded have normally have three parameters 1) Current bitrate, 2) Average Bitrate and 3)Peak bitrate. Though the DVD info shows 9.8Mbps (Peak), during real time playtime depending on the scenes (like action or fast moving sequences) the video bitrate changes. This method of encoding is done to maintain smooth playback of DVD in all DVD players and to avoid buffer underruns. The retail DVDs available in market have a average video bitrate between 4-5Mbps and peak touching in the range of 8-9Mbps.

Certain standalone DVD players (eg. Philips 5986) have the option of displaying video bitrate while the movie is played, shows the real time video bitrate of the movie and it changes according to the scenes.

@ajinkya - In other words the VLC player does not decide at what bitrate a particular scene will be played back. It is encoded in the DVD itself during the time of recording the same in the studio . VLC player and your graphics card may work in tandem to upscale the video if required using software but again that is a different story.