Video Median Capture - SD [VID-R1]

Record Type Digital Moving Images from Video Source Material
Expected Use Reproduction Master
Product Name Video Median Capture - SD [VID-R1]
Product Purpose

The purpose of this product is to respond to reference and reproduction requests.

Nature of Source Material

All standard definition video with or without sound not at risk due to deterioration or obsolescence.

File Properties Data Format


Capture Information

Target Total Bitrate: 50.8 Mbps

Timecode: Source LTC/VITC

Video data

  • Frame size: 720x480
  • Video codec: MPEG-2 MainConcept
  • Video bitrate: 50Mbps
  • Video mode: CBR
  • Video frame rate: 29.97 fps
  • Chroma subsampling: 4:2:2
  • 4:2:2 Profile, Main Level
  • Closed GOP, I-frame only
  • Lower field first
  • Interlaced scan
  • Single-pass encoding

Audio data

  • Audio channels: 2 (stereo L R)
  • Audio bitrate: 224 Kbps
  • Audio mode: CBR
  • Audio codec: MPEG Layer 2
  • Audio sample rate: 48 KHz
  • Audio sample size: 16 bit

Typical file size: ~ 360 MB/minute or 21.6 GB/hour

Possible File Derivatives

This master file can be used to create distribution files of equal or lesser capture quality.

Other Information

This product could also be used as a broadcast or production quality deliverable.

Audio and video levels may be adjusted as appropriate during the initial capture process but otherwise, the preservation files are unaltered. Reproduction and distribution files may have additional image improvements such as minimal color correction if necessary.

Quality Control Quality Assurance and Quality Control for MPEG-2 Format Products

NARA uses a commercially available, automated batch processing software tool to evaluate specific quality metrics. Below is a outline of our current processes for HD MPEG-2 formatted products. The exact aim point values are still in the testing phase. Once these values are confirmed, they will be added to this site. We continue to adjust our benchmarks and workflows as needed.

Color Bar Alignment
Color bar alignment is part of the manual video digitization workflow. Video levels are adjusted to original color bars on the source material when possible. When original color bars are not present on the source material, video levels are adjusted to the original content; setup and video level are the primary adjustments. Metadata is embedded into the video file indicating whether the source tape was adjusted to original color bars or the original content. The automated SAMMA workflow does not include color bar adjustment for individual tapes.

Embedded metadata compliance: NARA is working with FADGI to develop embedded metadata guidelines for reformatted video. They will be added to this site when complete.
Technical metadata: NARA uses its reVTMD schema for video technical metadata.

Customer Level Evaluation / Order Completeness

NARA is developing an in house job tracking order system to better coordinate work at the Branch level.

Item Level Evaluation: Automated File Characteristics Analysis
Fixity: NARA is evaluating workflows to create and validate checksums for each digital file.

Terms used in the QC protocols are defined in the Glossary of Terms

Category Technical Characteristic Warning/Pass/Fail or Logged Data
MPEG-2 File Format: Container Features
  • Video Tracks (number of)
  • Audio Tracks (number of)
  • Mismatch in Audio and Video Duration
  • File Size
  • Content Layout
  • PIDs Allowed for Audio and Video
Logged data
MPEG-2 File Format: Program Features Audio PID to Language Map Warning/Pass/Fail
MPEG-2 Video Essence: Video Description Features
  • Chroma Format
  • Frame Rate (Fps)
  • Picture Scanning Type
  • Scan Order
  • Frame Rate (Fps)
  • Resolution (Width/Height)
  • Resolution Change
  • Bits Per Pixel (Luma and Chroma)
  • Video Format
  • Average Bitrate (Mbps)
  • Duration
  • Pixel Aspect Ratio (PAR)
  • Display Aspect Ratio (DAR)
  • GOP structure
  • Active Pixels (Percentage)
Logged data
MPEG-2 Video Essence: Video Quality Features Video Signal Levels (Luma/Chroma) Warning/Pass/Fail
  • Color Bars
  • Black Bars
  • Freeze Frames
  • Brightness
  • Contrast
  • White Point
  • Cadence Break
  • Upconversion
  • Field Order
Logged data
MPEG-2 Video Structure
  • Profile
  • Level
  • GOP structure
  • Bitrate value (number)
  • Bitrate extension (number)
  • Top field first
  • Progressive sequence
  • Picture coding type
  • Picture structure
  • OP47 Data
  • Caption Data
  • Subtitles in Teletext PAL
Logged data
MPEG-2 Audio Essence: Audio Description Features
  • Sampling Frequency (Hz)
  • Bitrate (Kbps)
  • Frame size (bpf)
  • Audio Channels (Number)
  • Bits per sample (Number)
  • LFE Channels (Number)
  • Sampling Frequency Change
  • Bitrate change
  • Audio channel number change
  • Duration
Logged data
MPEG-2 Audio Essence: Audio Quality Features
  • Maximum Level
  • Audio Clipping
  • Test Tone
  • Average Level
  • Phase Mismatch
  • Level Mismatch
  • Loudness
  • Misplaced Channels
  • Background Noise
  • Transient Noise
  • Wow and Flutter
  • Jitter Noise
  • High Frequency Noise
  • Overmodulation
  • Silence
    • Lead-in
    • During recorded audio
    • Lead-out
Logged Data
MPEG-2 Audio Structure
  • Layer
  • Audio coding mode
  • Audio coding mode change
  • ID3 tag
  • ID
Logged data

For digital products created from video source material, the specifications are dictated to some extent by hardware and software capabilities.

Currently, the Video Preservation Lab creates uncompressed video streams in an AVI (Audio Video Interleaved) wrapper for the SD preservation master product option. All video is ingested on equipment that is calibrated to allow for ITU-R Recommendation BT.601 compliance, but also to allow for safe capture of graphics and other computer-generated materials that may contain luminance values in the superwhite range. This method of calibration and capturing supports the most authentic replication of the original source material.

  • The choice of a wrapper was one that NARA staff looked at very critically. According to an in-house international survey conducted in the spring of 2010 of over 50 institutions involved with film and video reformatting, the three main choices for preservation products were AVI, QuickTime (.MOV) or MXF (Material Exchange Format). Each has pros and cons. Based on the feedback we received, NARA has decided to use the AVI wrapper for a variety of reasons including:
  • Both the robotic capture system as well as the manual capture system can natively capture in AVI. (Only the robotic capture system has the option to capture in MOV; the manual capture system cannot natively capture in MOV.)
  • While the AVI wrapper has somewhat limited support for timecode, we are able to capture a start timecode from which the remainder of a timecode track could be generated if required.
  • AVI files are playable in a wide variety of open source tools including VLC.

We will continue to monitor codec and wrapper use within the professional community as well as toolsets development and reevaluate our products as needed, especially when HD video reformatting comes to the fore.

NARA’s options for reproduction masters are in line with peer institutions.

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