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Quality Comparison Chart

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How to record quality digital video.

What is digital video and what are the different recording methods and video file types?

Index

Video File types
Video Format vs. File Size
Mediums for Video Capture
Types of Capture Devices
Recording / Recording Media

 

Video File types

1. Digital Video - pictures in which strings of numbers represent color and pixel placement.

2. There are two kinds of video, un-compressed and compressed video.

AVI ~ Un-compressed video is represented by long continuous streams of numbers. This offers the best picture quality but the resulting file is enormous and most PC hard drives are unable to sustain the required data transfer rate. To give you an idea of how large this file size would be, if you were to take a typical DVD movie, and record it as un-compressed digital video (AVI), you would need upwards of 160Gigs. AVI is most commonly thought of as un-compressed video but it should be noted that other video formats also use the .AVI file extension as well, such as DV and MPEG4.

 Major types of compressed video files

* Compressed video is when complex equations are used to represent the long strings of numbers. This enables the file size to be considerably smaller.

MPEG1 ~ One of the oldest and most common types of compressed video is called MPEG1. This is the one used on VCDs and most commonly used for viewing video clips on a PC. The resolution of MPEG1 is 352x240 (or sometimes half that). MPEG1 is half the resolution of AVI but about 1/100th the file size.

MPEG2 ~ MPEG2 is similar to MPEG1 but has a resolution of 720x480. This equates to a video that is higher in resolution but typically four times the size.

MPEG is best designed for producing a very small file size for the amount of video data recorded. When recording video much information from frame to frame is the same. Particularly at lower data rates many frames are a merger of preceding and post frames. MPEG2 creates smooth video with a relatively small file size but if the video is paused it may result in a frame that looks quite blended between the two adjacent frames and a little blurred. To reduce this blurred effect the bit rate needs to be increased.

DV ~ One of the newer and most common types of video compression used by people with digital camcorders is DV. Unlike MPEG1 and MPEG2, DV records and compresses each frame independently of each other. It can sort of be described as if each individual frame was compressed as a JPEG. This does not create a file size as small as MPEG2 but can offer cleaner per frame video. This file type is great if you are concerned about the picture quality of individual frames. The individual frame quality is best seen during pause or editing of individual frames.

MPEG4 ~ One of the newest file types for recorded video is MPEG4, it capitalizes on the fact that for most video the picture information from one frame to the next is the same. MPEG4 compression uses this theory to help considerably reduce the file size without losing much picture quality. Imagine for a moment a stationary camera focused on a stand-up comedian on stage in front of a brick wall. The comedian changes positions with his speaking but the camera view of the brick wall remains the same. The video of wall does not change from frame to frame so should not need to be re-recorded. The compression engine as it is compressing can recognize un-changed video information (the wall) and record it as a note to see previous frame. Using this method can theoretically create a file much smaller with very little loss in picture quality.

 

 

Video Format vs File Size This is a chart indicating the time versus size difference between several formats. File Size * Compression Method 650 MB (CD-R) 4.7 G (DVD-R) 20 G 40 G 80 G 120 G AVI uncompressed 00:00:35 00:04:00 00:16:00 00:30:00 01:00:00 01:30:00 DV  00:03:18 00:24:00 01:20:00 02:40:00 05:20:00 08:00:00 MPEG-1 01:00:00 08:00:00 32:00:00 64:00:00 128:00:00 192:00:00 MPEG-2 00:20:00 02:00:00 08:00:00 16:00:00 32:00:00 48:00:00 MPEG - 4 05:30:00 44:00:00 176:00:00 352:00:00 704:00:00 1056:00:00                 *00:00:00 indicates hr:min:sec   *All the above data are approximate calculations based on the table below.   Compression Method Resolution Data Rate Compression Method Resolution Data Rate AVI 640 * 480 150 Mbps MPEG-1 352 * 240 1.15 Mbps DV  640 * 480 25 Mbps MPEG - 4 320 * 240 265 Kbps MPEG-2 720 * 480 4 Mbps MPEG - 4 720 * 480 1+ Mbps   *Mbps: Mega-bits per second (M bits/s)   *KBPS: Kilo-bits per second (K bits/s)

DV and MPEG4 alsouse the file extension of AVI

Mediums for Video Capture

AGP (VGA card with video-in/video out – VIVO)

PCI bus

USB 1.1 & 2.0

Firewire (IEEE1394)

PCI BUS ~ devices that use the PCI bus are usually PC cards that are plugged into the white slots on the motherboard or may also be an integrated chip on the motherboard. The great advantage with using the PCI bus is that with most applications you are not limited by data bandwidth. The disadvantages of using a PC card on the motherboard are; you need to open the case to install it, it requires system resources (an IRQ) and it may conflict with other installed devices. An empty slot needs to be available and the appropriate driver also needs to be installed.

USB 1.1 or 2.0 ~ is probably one of the easiest ways to connect a device to your computer. With USB you have the convenience of the device being portable and easily used on multiple systems. Unfortunately there is a major disadvantage to using USB. This is that the data stream is not consistent and is heavily dependant on CPU usage. USB has great peaks and valleys in data flow. We are not concerned with the peaks or the average. We are greatly concerned with the valleys. When these valleys drop below the minimum required data transfer rate this results in choppy video because of the missing data.  Newer software and the advent of USB2.0 has helped to reduced many problems that plagued USB1.1 video capture, but the problem of dropped frames and video/audio divergence still exists, particularly in the area of dropped video information. Video capture on USB is typically limited to a max data rate of 6mb/sec (mb = megabyte) and depending on the bit rate, a noticeable lag in data can be seen about every 3 seconds with USB1.1 and about every 12 seconds with USB2.0.  {Click Here to see Diagram}

Firewire IEEE1394 ~ Firewire offers many convenient similarities to USB. One great advantage that Firewire has over USB is that it is a much more stable media to transfer data. Although the actual average throughput of USB is much greater than that of Firewire, Firewire is not plagued with the great dips and pauses in data transfer as USB. This makes it an excellent medium for streaming video. If you want quality video without hiccups I would then recommend Firewire.

* Note - If you have an external hard drive and all you are concerned about is the speed of the file transfer, I would highly recommend USB2.0, as it is considerably faster than IEEE1394.

 

Types of Video Capture

Video Compression Methods

There are two main types of video compression. These are referred to as hardware and software compression. Some of you who are more tech savvy may know the difference between a hardware modem and a win modem. Software encoding means that a program uses the computer’s CPU to do the conversion between analog and digital. Hardware compression/decompression means that the device has a specialized chip on board, which is highly efficient at doing the conversion. These chips are so specialized and so efficient at doing the conversions that even the fastest CPUs typically lag when compared to dedicated devices,  (This is why high performance video cards have their own processors that take the load off the systems CPU). Another advantage of having a dedicated chip is that the chip is never called away to work on another task other than which it is working on. It is true that CPU’s are much more powerful than those of yesteryear, but the demand to record higher quality video has increased.  Even the newest, fastest CPU will be hard pressed to record full DVD quality in real time. Most video enthusiasts who were serious about recording video have a dedicated system for doing just that. Having a separate dedicated system avoids the problem of the computer CPU working on other programs while it needs all its resources dedicated to video compressing. Unfortunately most of us have multiple programs running in the background; many we may not even be aware of. Most of us are not at liberty to have an extra computer for just doing video. Constraints may consist of space, money, or a wife who does not approve of the additional computer clutter. For improved software compressing it is recommend that you shut down all unnecessary programs and disable others from starting to avoid poorly recorded sections of video. These poorly recorded sections occur when the CPU load exceeds the CPU’s ability. While this over load may be brief it still results as a glitch in the video.  
{Click Here to see Diagram}

The main advantage of software capture is the relatively low entry cost to capture video. A simple video capture card (without TV-tuner) can now be found for as little as $40 US dollars. Several new video cards now have the video capture ability built into them. Software capture also gives the most flexibility. With software capture you may capture into any one of the previously mentioned file types. To get the best quality video you can capture into AVI file format if you have a high performance hard drive that is A/V friendly, then use non-real time compressing to transcode the AVI file into another format such as MPEG2 or MPEG4. (DV may also be used as a good alternative as it is less demanding on the recording harddrive). This will give you the best video quality. Two disadvantages with this method are that it may take several hours to transcode the file and it is possible that after transcoding the audio and video streams will be misaligned. This will result in the video looking like a poorly dubbed foreign film. Newer software has improved and has been able to reduce this problem with better buffering. MPEG4 however is still very new and not yet standardized. Significantly more problems are involved in compressing to MPEG4 as compared to the older more established MPEG1 or MPEG2 formats. The transcoding time is heavily dependent upon CPU and hard drive speed, either or both could be the limiting factor depending upon the system used. This also means that transcoding can also be faster or slower than real time.

 

Types of Capture Devices

VIDEO INTO PC PORTS

CAPTURE DEVICES

Video capture card (PCI)

DV camera to IEEE1394 Firewire

Video to USB

Video MPEG2 compresser to USB

Video Capture Card (PCI) ~ often comes with TV-tuner

Advantages: The cheapest method of entry into the realm of video capture.  Most flexible in the types of files that you can capture, (AVI, MPEG1, MPEG2, MPEG4).  When you upgrade your system you still use this card on your new systems. Usually has pass through capability, this means that the option can be chosen to view but not record/compress video, during this viewing it places very little demand on systems resources. Best solution for internet cameras (net meeting).

Disadvantages: Compressing performance heavily dependent on system. Requires an empty PCI slot. You need to open your computer or have a professional install it for you (additional cost). It requires a driver and may conflict with other systems devices like the sound card. (Newer devices and drivers have reduced this problem.)

VGA CARD with Video Capture Capability (AGP-VIVO)

Advantages: Video Card and Capture only use the AGP slot. A PCI slot not required. Basically a Video card combo. Very flexible in the types of files that you can capture, (AVI, MPEG1, MPEG2, MPEG4).  Usually has pass through capability, video is not compressed so viewing video on the computer places very little demand on systems resources.

Disadvantages: Compressing performance heavily dependent on system. You need to open your computer or have a professional install it for you (at additional cost). You must take out your old video card. It requires a driver and may conflict with your other systems devices like your sound card. When you upgrade your Graphics Card you lose the capture capability unless you purchase another capture card. Using software capture, a divergence in audio and video may result but newer devices and drivers have significantly reduced this problem.

Video to USB device

Advantage:  Many times a USB device driver is identified by the OS and a driver is automatically installed from the operating system. USB is probably the most convenient input method and also offers the convenience of being portable and able to be easily used on multiple systems. Many USB devices are also advantageously very small. These make a good choice if your desire to only preview video or take a still frame snapshot. A USB 1.1 or 2.0 slot can be used to input video into the computer.

Disadvantages: Unfortunately there is a major disadvantage to using USB, this is because the data stream is not stable and is heavily dependant on CPU usage. USB has great peaks and valleys in data flow. If you desire to software capture video using a USB device you get a double whammy. Compressing Video puts a heavy strain on the CPU and the USB bus is also heavily dependent on the CPU. This is why you can see a dramatic performance hit changing from preview to recording.

Camcorder to Firewire

Advantages: Has many conveniences that USB has. If your PC is Firewire capable you only need to connect a cable from your camera to a Firewire port. Firewire is a much more stable medium to transport data and will not drop video information like USB.

Disadvantages: Digital camcorder is required. Compressing is heavily dependent on system speed. Video capture may be less than real time. Using software capture a divergence in audio and video may result. Newer software has reduced this problem somewhat.

USB 2.0 External Hardware MPEG 2 Compressor Capture Device

Advantage: Not so limited by systems performance, having an external compressor has many of the conveniences of USB. The compressing of video is not dependent upon the CPU. You can do other tasks (with moderation) while you are compressing video. USB 2.0 has far fewer streaming data lags as USB 1.1. The resulting file is small and is in the same format as that seen on DVDs.

Disadvantage: Requires a USB 2.0 port. Will periodically drop some video as is inherent with streaming video across USB. 2.0.  Requires an external power source.  Considerably more expensive than other solutions.

PCI MPEG1&2  Hardware Compressor

Advantages: Not limited by systems performance. Not limited by bandwidth problems like other devices.  Resulting file a very good balance between picture quality and file size.  Can be used with some older computers. Resulting file is the same type used on VCDs or DVDs. Quality video file can be burned real time onto a DVD in standard DVD format. Traditionally a very expensive device but now much more economical units exist. Audio and Video are always aligned. If you upgrade your system the device is to be put on your new computer.

 Disadvantage:  Not as flexible in capturing different file formats such as AVI or MPEG4.  More expensive than other video capture methods.

 

Recording

DVD players read the file type known as MPEG2. They are also able to read the older VCD file type of MPEG1. When creating a DVD video on your PC to be read on a stand-alone DVD/VCD player you need to use DVD or VCD burning software. This is because the DVD/VCD player requires additional files in order to know how to read and open the MPEG2 or MPEG1 files.

 * If you just record the file on to a disc it can still be read by a PC but not by a stand-alone DVD/VCD player. In the proper format most DVD players can read MPEG1, MEG2, CD audio tracks as well as some newer players can also read MP3s.

Update: There are now a few stand-alone DVD players on the market that can play MPEG4 (DIVX).

Recording media:

For recording quality audio/video there is variation in the different drives and even more so in the recording media. For A/V it is recommended you purchase a quality drive.

For interface we recommend internal SCSI or IDE connections. For External solutions it recommend you use SCSI or Firewire IEEE1394. It is not recommend using USB 1.0/2.0 for audiovisual recording/playback as it has inherent data lags that result in video hic-up. {See USB interface in above article}

VCDs and SVCDs can be recorded on a standard CD using a typical CD-writer. A VCD uses the MPEG1 file format, and an SVCD uses a modified MPEG2 file format. For the same amount of video time an SVCD file is about 50% larger than a standard VCD.  {To see the different media recording times look at the above chart.} You can record DVD video on to a CD. This is called a mini DVD and holds about 20 min.

 Recording Standards: DVD-R, DVD-RW, DVD+R, DVD+RW

The two main standards for recordable DVDs are DVD-R & DVD+R  

* an additional W at the end means that the disc is rewritable.

 DVD-R ~ is the original DVD writer format and is said to be more compatible with older DVD players.

Current max speed of DVD-R writers is 8x

 DVD+R ~ is a newer DVD writer format and is said to carry greater compatibility, especially with newer DVD players. The immediate disadvantage of this format is that the DVD writers are more expensive as well as the cost per disc. This cost is about 25% more for both the machine and per disc. This may change as the prominence of DVD+R increases. Current max speed of DVD+R writers is 8X.

DVD-RW ~ only supports write-at-once

DVD+RW ~ allows individual changes to files on the disc
{Supports on disc video editing}

 4.7Gig & 9.4 Gig DVDs

There are two types of commercial DVDs. These are called dual and single layer. A single layer DVD can hold 4.7 Gigs, a dual layer DVD can hold twice that. The most common DVD writers on the market can only create single layer DVDs. Because of this it creates some interesting issues. A stand-alone DVD player may try read a single layer DVD-R/DVD+R as VCD because of its single layer. When reading the disc, it looks for a second layer; if it cannot find the second layer it returns an error message. To overcome this issue it is recommended that you download a patch or use newer software that tricks the player into thinking the disc is a VCD while the disc retains its true file size and resolution. Another issue is, you that cannot record a 9.4Gig DVD directly on to a 4.7Gig DVD-R. If you want to record DVD video files to another drive you need what is called DVD ripping software or re-record the file. The first solution is a good method is good if it you have a lot of time and a very fast PC as the ripping process is typically much slower than video playtime. Another method you could use is to use hardware to re-compress the DVD. This solution works in real-time and when re-compressing the DVD you can set the bit-rate to insure the most efficient file size to fit on to a DVD-R or DVD+RW. For this solution we would recommend using a quality hardware MPEG2 compressor. These solutions are great not only for back-ups but they also eliminate any region locks on the DVD as well.

Update - Sony and some other companies now make dual layer DVD recorders, these are able to record 9.4 Gig onto a single recordable disc.

* Piracy is not advocated and this information provided as the best way to make back-up copies only.

Any Comments or Questions?  Please email me at tstatser@cestuff.com