MPEG-4 — Copying a DVD Video to CD-ROM — THG.RU

Compressed: DVD Video on a CD-ROM

What we are presenting here is almost a sensation. Just imagine: With the help of a small tool it is possible to store the content of complete DVDs on a CD-ROM without any noticeable loss of quality. This makes buying an expensive DVD burner with limited memory capacity obsolete. On top of that: The nifty program can be downloaded from the Internet for free and is quite versatile.

To copy a video with up to 9 GB from a DVD to a CD-ROM requires a lot of computing power and time. After all the data volume must be reduced to about a 12th of its original size to accommodate the 700 MB of limited storage capacity of the CD-ROM. A data compression of this magnitude for digital video is only possible with the new video compression standard MPEG-4. Generally speaking MPEG-4 is an extension of the MPEG-2 technology, but MPEG-4 can be used more universally.

The history of MPEG goes back to the year 1987. MPEG stands for Motion Pictures Expert Group, a worldwide organization that develops manufacturer and platform independent standards for video compression. The first result was introduced as MPEG-1 in 1992. It was the basis for the less successful European Video-CD. Because of its limited resolution of 352 x 288 pixels, MPEG-1 is only suitable for the home environment, and the achievable video quality in relation to the data rate is rather low from today’s point of view. MPEG-2 was introduced in 1995 and is mainly based on MPEG-1. The higher resolution with a maximum of 720 x 576 pixels is a major improvement enabling a significantly better video quality. The newest format is called MPEG-4 and was released by the MPEG group only recently in December 1999.

A movie sequence from a DVD generally comes in MPEG-2 format. This part is from the movie blockbuster «Matrix» and played back on the Mediaplayer.

This is the same video sequence in MPEG-4 format. Differences in quality are hardly noticeable, even though the data volume is only about 1/11 the size of the original MPEG-2 video.

MPEG-4: High Video Quality at Low Data Rates

MPEG-4 comes with a few important improvements compared to the older and established video compression technologies like MPEG-1 and MPEG-2:

• independent encoding of pictures and video
• increased encoding efficiency, more efficient compression of pictures, video and textures
• very variable resolutions
• scalable complexity
• extended error correction
• increased flexibility for object-based encoding
• small buffer delay
• Global Motion Compensation (GMC)
• content-dependent scalability of textures

This table displays the individual MPEG technologies. The fact that MPEG-4 runs at a low data rate despite offering a high resolution is quite noticeable.

Similar to MPEG-2, MPEG-4 also consists of different profiles. This allows adapting the audio/video stream to the actual application. MPEG-4 takes into account the special requirements from the computer, telecommunication and television areas. It encodes not only rectangular pixels but also individual objects of a scene. Here is a little example: A vehicle drives in front of a specific background that hardly changes. While the whole picture is encoded in many rectangular images, the vehicle can be separated as an object and treated as a sprite in front of a fixed background.

FlaskMpeg — A DVD Copy, Please!

A very interesting program called «FlaskMPEG» is capable of converting complete movies from DVD into the space-saving MPEG-4 format. The tool can be downloaded for free at the FlasK MPEG Home Page. We thoroughly tested this program, and we are very satisfied with the video quality it offers. And this is how it works best: First all data are copied with the extension .VOB (Video Object File) to the hard disk with an appropriate tool. Afterwards the program Flask Mpeg is started.

We have to advice you here, that copying of copyrighted material and redistribution is illegal! However, some countries allow private copies for home use. Therefore, you have to check what law applies in your country in the first place. Luckily you don’t have to worry if you experiment with free DVDs or your own digital videos.

Resolution, picture refresh rate and iDCT options of the MPEG-4 video are set in this menu. However, do not expect large increases in speed when activating the MMX function.

Another menu of the Flask Mpeg encoder: The selection «HQ Bicubic Filtering» causes a relatively big data stream. For compact file sizes the setting «Nearest Neighbor» is recommended.

This menu shows the selection for the audio signal quality. The selected option encodes the audio part in MPEG-1 layer III.

Divx 😉 — the best MPEG-4 codec under Windows 98/2000

A special software codec is necessary for playback of the recorded MPEG-4 sequences. Even though the files put out by Flask Mpeg have the ending .AVI they are definitely MPEG-4 files. Currently Divx is the best codec, which is available as Freeware under DivX 😉. The audio/video drivers for MPEG-4 playback are added as plug-in to the existing Microsoft player (included in the operating system of Windows 98 SE or Windows 2000).

Divx is currently the best software codec for MPEG-4.

The software codec (Divx is shown in the picture) is accessed during playback of a MPEG-4 file.

The Divx codec can be adapted to the individual requirements. But be careful: The CPU load is always very high.

This picture shows both the MPEG-4 codecs for video that are found in the system control.

One thing must be made very clear at this point: Playback of MPEG-4 encoded video movies requires very sophisticated hardware. In our test we used a system containing an AMD Thunderbird with 800 MHz and 128 MB of memory. After all, at full screen playback (1024 x 768 x 16) of the video encoded with 720 x 576, the CPU load under Windows 2000 was almost at 80 percent. However, friends of socket7 platforms are going to be disappointed: When we tested it with an AMD K6-2/450 the playback was not smooth.

Encoding MPEG-2 files with the FlaskMpeg program requires even more computing power. Completely converting a DVD video into MPEG-4 format usually takes about 10 hours. Again, the speed greatly depends on the processor used. Otherwise the system requirements for converting video from MPEG-2 to MPEG-4 format are relatively low.

Requirements for copying DVDs

• PC system with DVD-ROM drive (country code perhaps enabled)
• Processor from 450 MHz, because of high computer power requirements
• Windows 98 or Windows 2000
• Flask Mpeg and Divx software codec

This image shows the details of a video film encoded in MPEG-4. This file runs over 108 minutes with full resolution, only takes up 698 MB and thus fits on a CD-ROM.

High picture quality despite high resolution: This sequence is from a movie and has a data rate of 110 KB per second.

Comparison of MPEG-2 and MPEG-4

Among the MPEG technologies used in practice, the current MPEG-4 offers the highest efficiency during encoding. The main reason is ACE (Advanced Coding Efficiency) — an encoding algorithm that is used in MPEG-4 for the first time.The object orientation in connection with ACE enables very low data rates. It allows storing a complete video movie in full PAL or NTSC resolution and stereo audio (16 bit, 48 kHz) on a single CD-ROM. For clarification: 700 MB of storage is totally sufficient for most movies that run up to 110 minutes. A movie in MPEG-2 format, on the other hand, requires at the same resolution about 11 times more storage space (DVD with 8 GB). While the data rate of MPEG-2 is coupled very closely to the actual profile, MPEG-4 is scalable over a wide area in the audio as well as in the video stream. Audio signals can be processed from 2 Kbit/s to 24 Kbit/s while video is variable between 5 Kbit/s and 10 Mbit/s. Because of this scalability the audio/video data can be adapted specifically to the actual environment. MPEG-2 is mainly used for the large applications: as data format on a video DVD, as data stream in digital television broadcasts and in video editing for digital video broadcasting.

Applications for MPEG-4

There is an almost unlimited number of applications for the new video format MPEG-4: The home user can store MPEG-2 videos on a CD-ROM. For example it is now possible to convert DVDs into MPEG-4 format at the home PC to play them later on the notebook (without DVD-ROM drive). Audio signals may be broadcasted over the Internet with MPEG-4 compression for «audio on demand». This Digital Audio Broadcasting is possible because it only needs about 16 kbit/s bandwidth. The situation is similar for video services and animations of 2D or 3D objects that can be send over the Internet with different data rates simultaneously. The new mobile radio standard UMTS is also based on MPEG-4 compression technology.

MPEG — Quick Outlook

MPEG-4 is the current state-of-the-art for video compression technology. The two older technologies MPEG-1 and MPEG-2 already caused a widespread distribution of digital video on the PC and notebook. The successor of MPEG-4 is already on the horizon and is called MPEG-7. This video standard is supposedly going to be introduced in July 2001 and principally integrates an object search routine. MPEG-2 will also be extended; MPEG-21 is the succeeding standard.

Conclusion: MPEG-4 — a very efficient and universal video format

One thing is certain: With its low data rate combined with comparatively high video quality, MPEG-4 revolutionizes the market for digital video. MPEG-4 offers better compression algorithms than MPEG-1 and MPEG-2. However, encoding of a MPEG-4 sequence requires a lot of computing power: With the Flask Mpeg program even a fast PC takes several hours to convert a movie in MPEG-2 format. But the quality is very respectable: At a selected data rate of 110 KB per second the copy hardly differs from the original.