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Why we will carry through video compression and conversion? I think this is most beginners will be asked questions. The following is my personal perspective analysis:

One reason: most manufacturer of portable device for video format support is limited. Like as phone manufacturers may only support 3GP, MP4 format, a small number of support AVI, and other formats.

The second: it will be carried out between the conversion for the limited support format when most prevail video file is RM, MPEG, DVD, and other formats, therefore,if you want play on your portable, you should convert them with third tools.

Okey, some people may ask me why the file is 3 GP format, MP4 or AVI now , and my portabel also support this files , but it doesn’t play on my portbale? most of the reasons is beyond video bit-rate,so general re-establishment can be resolved.

After all, our mobile equipment capacity is limited,therefore, in terms of guaranteeing the clear and fluent video, we must minimize file size in order to allow more capacity.

In this article，I will discuss mainly video conversion and compression will relate to knowledge，like as the Video codec、video bitrate.ect.

Whether you use any conversion software you will encounter the following three terms：

Video codec:

A video codec is a device or software that enables video compression and/or decompression for digital video. The compression usually employs lossy data compression. Historically, video was stored as an analog signal on magnetic tape. Around the time when the compact disc entered the market as a digital-format replacement for analog audio, it became feasible to also begin storing and using video in digital form, and a variety of such technologies began to emerge.

Audio and video call for customized methods of compression. Engineers and mathematicians have tried a number of solutions for tackling this problem.
There is a complex balance between the video quality, the quantity of the data needed to represent it, also known as the bit rate, the complexity of the encoding and decoding algorithms, robustness to data losses and errors, ease of editing, random access, the state of the art of compression algorithm design, end-to-end delay, and a number of other factors.

Framerate:

Defines how many pictures eg. frames one second of video or audio contains, normally used acronym for framerate is fps - frames per second. Human eye can't see picture changes after the framerate is more than ~24fps.

In motion pictures, television, and in computer video displays, the frame rate is the number of frames or images that are projected or displayed per second.

Frame rates are used in synchronizing audio and pictures, whether film, television, or video. In motion pictures and television, the frame rates are

standardized by the Society of Motion Picture and Television Editors (SMPTE). SMPTE Time Code frame rates of 24, 25 and 30 frames per second are common, each having uses in different portions of the industry. The professional frame rate for motion pictures is 24 frames per second and, for television, 30 frames per second (in the U.S.).

In computer video streams, the frame rate describes playback rates for AVI and QuickTime movies. The video playback rate for an AVI or QuickTime movie directly relates to the perceived smoothness of its playback. The higher the number of frames playing per second, the smoother the video playback appears to the user. Lower rates result in a choppy playback. (As a reference point, film uses 24 frames per second to allow the viewer to perceive smooth playback.)

Several factors affect the actual frame rate you get on your computer. For example, your PC processor or graphics hardware may only be capable of playing 10-15 frames per second without acceleration.
In developing motion pictures, television, and video, frame rate information is used as a reference for audio signals. The recorded signal includes information about location in time using a 24-hour clock, and individual frame numbers. This signal is used to synchronize multiple audio and video machines during the recording and editing process. Using a master synchronizing device, the operator can issue location commands from a central machine and have all slaved machine follow the master.

Bitrate:

Bitrate refers to the size, over time, of a video or audio stream. Although most computer oriented applications measure bitrate in terms of binary kilobits and Megabits where 1kb (1 kilobit) = 1024 bits and 1Mb (1 Megabit) = 1024 kilobits, bitrate calculations use standard metric values for these prefixes, meaning 1kb = 1000b and 1Mb = 1000kb. Bitrate calculations are typically made in kilobits per second (kbps) or Megabits per second (Mbps). They can also be expressed in other units, including bits per second (bps) or even Megabytes per second (MBps). Notice the capital B denoting Bytes. You should always use a lower case b to denote bits and upper case for Bytes.

As my experience，if you want get the best compression proportion, depends the video bitrate and framerate.

The following is IPOD supports format:

iPod classic：

Audio
Frequency response: 20Hz to 20,000Hz
Audio formats supported: AAC (16 to 320 Kbps), Protected AAC (from iTunes Store), MP3 (16 to 320 Kbps), MP3 VBR, Audible (formats 2, 3, and 4), Apple

Lossless, WAV, and AIFF
User-configurable maximum volume limit
Video
H.264 video, up to 1.5 Mbps, 640 by 480 pixels, 30 frames per second, Low-Complexity version of the H.264 Baseline Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; H.264 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Baseline Profile up to Level

3.0 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats

iPod nano:
Video
H.264 video, up to 1.5 Mbps, 640 by 480 pixels, 30 frames per second, Low-Complexity version of the H.264 Baseline Profile with AAC-LC audio up to 160 Kbps,

48kHz, stereo audio in .m4v, .mp4, and .mov file formats; H.264 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Baseline Profile up to Level 3.0 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames

per second, Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats
Audio
*Skip-free playback
*Frequency response: 20Hz to 20,000Hz
*Audio formats supported: AAC (16 to 320 Kbps), Protected AAC (from iTunes Store), MP3 (16 to 320 Kbps), MP3 VBR, Audible (formats 2, 3, and 4), Apple

Lossless, AIFF, and WAV
*User-configurable maximum volume limit

refer to:http://www.apple.com/ipodshuffle/specs.html


Therefore，if you want put the video on your iPod Touch, make sure the video formats are as follows:
H.264 video, up to 1.5 Mbps, 640 by 480 pixels, 30 frames per second, Low-Complexity version of the H.264 Baseline Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; H.264 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Baseline Profile up to Level 3.0 with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats; MPEG-4 video, up to 2.5 Mbps, 640 by 480 pixels, 30 frames per second, Simple Profile with AAC-LC audio up to 160 Kbps, 48kHz, stereo audio in .m4v, .mp4, and .mov file formats.


In this way, when you know the knowledge, the conversion will no longer be any difficulties thing, as long as you read user manual or surf Internet to find which format will be supported, then convert them will so easy!!

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Posted: 2008-01-22 08:01:37
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Oh ,GOOD!
Guys,
I want to know where Ipod video can catch from?
How can I get them to my Ipod?

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Posted: 2008-01-22 08:11:56
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OK, you mean convert video to portable playback devices (iPod) supported video format: 3gp, mp4?
Actually, there are some kinds of such video to 3gp tools currently. If you search on google, you'll find many such product. In my point of view, I recommend you this one: Moyea video to iPod converter.
Moyea Video to iPod Converter is a utility program. It can help you convert all popular video and audio formats including AVI, MPG, MP3, MP4, VOB, MOV, AAC, WMV, WMA, 3GP, 3G2, DV, AAC, M4A, etc. to iPod supported formats.
Besides the function of file conversion, this converter has many other functions, such as video editing. You can get the fit style by setting some parameters and using the functions of cropping video, trimming video and adjusting effect. You may also set your preferences settings, and apply the format settings, like video bit rate, video size, video and audio codec, etc. to all the files on the list with only one click.
you can learn more at: http://www.my-video-converter.com/video_to_ipod/
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Posted: 2008-01-22 08:24:25
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Hi,i think you can google such tools:)
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Posted: 2008-01-22 08:44:25
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Hi,guys,this tools i also using:)
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Posted: 2008-01-24 09:15:33
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Thank you for share,i see more:)
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Posted: 2008-03-03 02:30:04
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