Audio-visual archives digitized data storage format
In the management of audio-visual archives, mainly for photos, video, audio file object management, in order to facilitate the preservation and re-use archives, records management departments began to use each now powerful multimedia technology and computer technology, the audio-visual archives digital, but different digital standards and file storage format, digitized archive quality difference is very large, you can file for a different purpose, using different digital solutions.
Audio-visual archives digitized for the purpose of long-term preservation and re-use, for long-term preservation, digitized archives must be close to a true reflection of all the features of the original file, and archive data files such digitized particularly big, not easy to archive data retrieval, therefore, when we digitized audiovisual archives, archives of each generate two digital files, one for long-term storage, for retrieval. Data files for retrieval is very small, so when retrieving on low-bandwidth Internet, you can guarantee fast data response, the user retrieved audio-visual archives, you can watch the video screen directly through the Internet, pre-listen to the sound, when needed the original archive data file, through authorized, can be downloaded to the machine to use.
An archives generate two digital files, do not need two digital, audio and video archives when digitizing, archiving class can directly generate digital files with a high sampling rate, on the basis of this document, through the conversion process, you can any sampling rate to generate a low-level data files to retrieve.
1．Photos digital storage format and parameter settings
Photos digitized image storage format are many, for archived class photos in TIFF format is recommended, but a lot of photos directly from digital cameras to store the JPEG format can also be used directly for archiving. TIFF is a flexible image storage format can store color, grayscale, binary image. For color images, support for RGB and CMYK modes, RGB (red, green and blue) we are more familiar, CMYK (cyan, magenta, yellow, black) is a storage format designed for printing, a large number were adopted in the printing industry. In terms of data storage organization, supporting uncompressed storage, LZW lossless compression memory; the binary image also supports CCITT Group4 lossless compression storage.
When the scanned image file, as long as the scanning resolution is high enough, you can almost entirely reflect the original photo. But limited by the resolution of scanning hardware, storage space constraints and some hardware constraints, we can only choose an appropriate scanning resolution, below the correspondence between several scanning resolution and storage space.
TIFF RGB Uncompressed format：
There is sufficient storage space, it is recommended to store photos with 1200DPI scanning.
Preview photos of generating：
After the original archive image generation, through software, it can automatically extract for previewing images. Here again, what comes to the preview image storage format to use, how high resolution adopted problems. Preview images to be able to see the image on a computer content to the principle of a resolution as low as possible, by experiment that, using 72DPI better resolution, this resolution can only see the image of the whole picture, but also guarantee a minimum of storage space. On the storage format, using JPEG compression and storage, to save storage space.
Use 72DPI, JPG compression quality storage medium, different size photos of storage space in the following table：
2．Digital video storage format and parameter settings
For storing video image data format are many, some suitable for archival storage, some adapted to network online play. For archival-quality video images, the proposed compression MPEG-2 compression algorithms, MPEG (Moving Picture Experts Group) is a famous international digital video and audio compression standards organizations, its series of standards MPEG-1, MPEG-2 , MPEG-4, MPEG-7, etc., these standards have been broad support different hardware and software vendors, different standards apply to different application areas, not to say that after the standard sequence numbers the better. Such as MPEG-1 is VCD compression standard that can compress video only achieve quality home video recorder; MPEG-2 is a DVD and digital television transmission compression standard; MPEG-4 compression standard video streaming, its compression efficiency higher in the case of low-bandwidth network, ensure continuous video data playback is currently a lot of VOD (video on demand) used; MPEG-7 multimedia content description interface, providing content-based video retrieval mechanism can be directly retrieve a video camera.
With MPEG-2 compression to store archived grade video archives, video sampling data flow 10Mbps, audio sample data flow 384Kbps, 48KHz, stereo, video screen resolution of 720 × 576, so one hour of video footage, the MPEG-2 compression after accounting with 4.2GB of storage space, if need backup, just to back up onto a DVD disc. MPEG-2 compressed data file, can be directly used for playing, editing different purposes.
Generate a preview video data stream：
For previewing video data stream must be streaming media formats to meet the needs of network online play. The most commonly used streaming formats, in addition to MPEG-4 mentioned above, there are Microsoft's ASF (Advanced Streaming Format), WMV (Windows Media Video), RealNetworks company's RM / RAM / RMVB and other video data formats, these video data formats are particularly popular on the Internet, have strengths, supported software and hardware are also particularly high. MPEG-4 moving image restore some better, WMV reduction of color is better, a higher compression quality RM / RAM / RMV, in the case of a low-bandwidth network, you can still get a good playback performance.
Because of Microsoft's dominance of the software industry, and its related production and playback software more accessible, recommendations preview video stream using WMV compressed storage format, you can generate directly related to the level of conversion software from archived video data file in the case you can see the contents of the data file preview of the smaller the better.
WAV compression parameters: Video data compression rate using 256Kbps, the video screen resolution of 320 × 240, so one hour of video footage, WMV format with storage, accounting with 110MB of storage space.
3．Audio digital storage format and parameter settings
Currently the format for audio data storage lot, such as WAV, MIDI, MP3, Ogg, Dolby AC-3 and so on. For archived audio file level, or the use of storage WAV format, WAV format developed by Microsoft waveform storage file, since Microsoft's dominance in the software industry, the format is very popular and popular, it is non-compressed, the sampling rate is sufficient under high, you can accurately record sound.
When recording WAV files, usually selected two-channel stereo, 16 samples (each sample point around 16 channels each), the sampling rate is a very important parameter, generally choose 48Khz, can achieve the effect of broadcast, You can also use 44.1Khz, you can achieve playback quality of the CD. WAV file for this parameter is set, the recording audio data accounted for about one hour with 600MB of storage space.
Audio data stream generated preview：
Similar processing video data stream, audio data stream for preview must also be streaming media format, currently used mainly audio streaming formats MP3, WMA, RM / RAM / RMVB formats. MP3 is actually MPEG aforementioned third voice compression layer (Audio Layer-3) for audio compression algorithm, the network is very popular. WMA (Windows Media Audio) is a Microsoft audio compression streaming media format, RM / RAM / RMVB mentioned earlier.
Since a large number of popular MP3 standard and its openness, preview audio data stream is recommended to store the MP3 format, MP3 files when extracting data stream rate is set to 56Kbps, record audio data accounts for one hour with 25MB of memory space.