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Formatting video for local playback

Generated by Clearspace on 2008-05-18-05:00

5

Resolution

Both visible and audible information are naturally analogue mediums. This analogue information must be sampled to
be stored digitally. The number of samples dictates the resolution of the digital copy, with more samples improving
the resolution and definition. Within the scope of this document and its purpose, there are only four digital sample
resolutions that are relevant. The first is the visual resolution of the video stream, measured in pixels as width by
height, comparable to resolution of your computer display. Higher pixel resolution permits more detailed images. The
visual resolution also dictates the aspect ratio of the video. Aspect ratio is the ratio of width to height, typically 16:9
for widescreen video, and 4:3 for standard video.

The second is the temporal resolution of the video stream; the frame rate, measured in frames-per-second (fps). It
affects the perceived smoothness of motion in the video. With the aid of motion blur and similar effects that make use
of how our eyes perceive movement, 24 fps is the minimum to produce perfectly fluid motion on any scene, and is
the standard for feature films. Slightly lower frame rates are still quite smooth to the eye for many scenes, down to
around 20 fps, below which a staggered effect on motion is ever more easily perceived by the viewer.

The third resolution of importance is the temporal resolution of the audio stream; termed sample rate, and measured
in kilohertz (KHz). It governs the maximum sound frequency (as in pitch) the digital audio stream can contain. To
reproduce a sound in a digital copy, the sample rate must be at least double the frequency of the sound. 44.1KHz
and 48Khz are the main sample rate standards in multimedia video, therefore covering frequencies beyond the upper
audible range of 20KHz.

Finally there is also the directional resolution of the audio stream, measured by the number of channels present in
the audio. A single channel is a mono recording, while two channels afford stereo sound. Increasing channels further
to 4 or 5 allows fully directional surround sound, for example, 5.1 surround sound uses 5 channels in a digital audio
stream.

Compression

To reduce storage requirements and improve portability, data streams in digital video are usually compressed. Each
stream is passed through a compression algorithm, referred to as a codec (COmpresser/ DECompressor). Separate
codecs are used for video and audio streams, as each stream has quite different characteristics.

The act of compressing a stream is known as encoding. In order to play back a compressed stream, it must be
decoded. Therefore the playback hardware must support decoding of the compression codec used. Converting an
already compressed stream from one codec to another codec is termed transcoding.

Compression is usually 'lossy', meaning that some data is lost and the compressed stream is not a bitperfect copy of
the original. Whether the effect of these 'lost' bits of data is perceptible upon playback depends greatly on the type
and amount of compression used. Data loss from high compression levels can introduce perceptible noise and other
distortions into a stream, and these noticeable effects are termed compression artefacts.

Compression amounts are set by the amount of data assigned to the stream, typically measured in kilobits\-
per-second (kbps), and referred to as bit rate (as in the rate of bits assigned). Compression codecs often have
sub-features that extent or improve their performance. It is important to note that some playback devices do not
support certain features of a codec. To make the compatibility of these features easier to manage and understand,
most codecs have profiles and/or levels describing which features and parameters can be used.

For example, MPEG-4 video can be encoded in Simple or Advanced Simple profiles in levels of 0 to 5, with simple
profile level 1 being used for video on mobile phones, and advanced simple profile levels used on most web video
content. Another example is WMV video, which comes in profiles such as WMV8, WMV9, and WMV9.1.

Summary of Contents for D750

Page 1: ...competence required to follow this document extends only to basic computer skills as all concepts are fully explained Prior experience with editing or formatting digital video is advantageous Sony Ericsson mobile phones that are covered by this document Generic names series Sony Ericsson Mobile Phones K800 K800i K800c K800a K790 K790i K790c K790a K750 K750i K750c D750 K610 K610im K610i K610c K618i...

Page 2: ... track up to the point just before distortion or clipping will occur Bit Rate The number of bits used to compress a data stream typically measured in kilobits per second kbps Codec COmpressor DECompressor an algorithm that compresses and decompresses data streams Container The package that video and audio streams are placed in to ensure synchronised playback Data Stream The encoded video data Deco...

Page 3: ... as MPEG 4 or H 263 and audio streams as AMR NB or AAC LC formats 3GPP 3rd Generation Partnership Project 3ivx A commercial video codec suite that allows the creation of MPEG 4 compliant data streams AAC Advanced Audio Coding AAC LC Advanced Audio Coding Low Complexity AC3 Audio File Format AIFF Audio Interchange File AMR Adaptive Multi Rate NB NarrowBand WB WideBand AVI Audio Video Interleave Con...

Page 4: ...ofile features Trademarks and aknowledgements Vegas is a trademark or registered trademark of Sony Corporation Microsoft and Windows are either registered trademarks or trademarks of Microsoft Corporation in the United States and or other countries Apple QuickTime and Final Cut are a trademarks of Apple Computer Inc registered in the U S and other countries Premiere After Effects and Audition are ...

Page 5: ...er of channels present in the audio A single channel is a mono recording while two channels afford stereo sound Increasing channels further to 4 or 5 allows fully directional surround sound for example 5 1 surround sound uses 5 channels in a digital audio stream Compression To reduce storage requirements and improve portability data streams in digital video are usually compressed Each stream is pa...

Page 6: ...compression with AAC compression for audio Similarly WMV files are Advanced Systems Format ASF containers using WMV video streams and WMA audio streams AVI files are Audio Video Interleave containers that use Video For Windows compatible codecs for video streams and generally WAV or MP3 audio streams Formatting video for Sony Ericsson phones This section contains specific details and recommendatio...

Page 7: ...sson phones only support level 0 With some customisation of the suggested values Sony Ericsson phones can also support modified levels up to level 3 There are many implementations of the MPEG 4 visual codec with quite extreme differences in encoding quality Available MPEG 4 codecs include DivX XviD 3ivx Apple MPEG 4 Nero MPEG 4 and many standard implementations found in various video editing softw...

Page 8: ... 15 15 Bit rate kbps 64 64 Optimal video XviD MPEG 4 Visual Simple Modified Level 2 XviD MPEG 4 Visual Simple Modified Level 3 Video resolution 176x144 QCIF 320x240 QVGA Frame rate fps 20 25 Bit rate kbps 140 300 Basic audio LC AAC LC AAC Channels 2 2 Sample rate KHz 44 1 48 44 1 48 Bit rate kbps 64 64 Optimal audio Apple Nero LC AAC Apple Nero LC AAC Channels 2 2 Sample rate KHz 44 1 48 44 1 48 B...

Page 9: ...n MP4 container it is recommended to output multimedia video in the MOV format The MOV format allows the multimedia video to be easily opened by Quicktime Pro Other considerations The following is general advice to achieve better results when formatting multimedia video for Sony Ericsson phones Sony Ericsson phone screens have a 4 3 aspect ratio The visual resolution of the source media may be of ...

Page 10: ...solution and aspect ratio in order to address the issues of correcting them within this example Note Please consult the relevant licenses for any software before using it for commercial and or personal purposes Software Required software The following software is needed to complete this tutorial Microsoft Windows 2000 or Microsoft Windows XP as operating system Make sure the latest service pack is...

Page 11: ...h 16 4 Click the Ok button to create the new project Importing the source video and formatting track properties 1 Return to the menu and select File Import Media 2 Browse to your working directory and open the SEexample avi file 3 Select SEexample avi in the Project Media window and drag it to the track list the empty panel on the left above the Project Media window The video and audio tracks with...

Page 12: ...t or press ctrl e The Save exported file as dialog will appear 3 Set the Export option to Movie to MPEG 4 4 Now click the Options button and the MPEG 4 Export Settings dialog will appear 5 Set the File Format option to MP4 6 Ensure the topmost drop down menu is set to Video and set the following Video Format MPEG 4 Improved Data Rate 140 kbits sec Image Size Current Frame Rate Current Key Frame Ev...

Page 13: ...ality at which the multimedia video content is delivered Those with no prior experience of editing or formatting digital multimedia video will hopefully find the background information sufficiently enlightening such that they can understand the more specific requirements of Sony Ericsson phones and feel confident about the task of formatting multimedia video for them Software developers can access...

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