Topic 1 - Digital Files

Peter Bubestinger

File Format Considerations

The Goal

The Holy Grail

* Best quality * Preserve original properties * Last forever * Lowest size * Fast and easy to open/use * +cherries & ice cream on top * …

Data Structure

Hex view of WAV header (annotated)

Digital Video Trinity

What’s inside?

MediaInfo’s “Easy” view

Characteristics

Image

File 1 File 2 File 3
Format TIFF 6.0 TIFF 6.0 TIFF 4.0
Colorspace RGB CMYK Grayscale
DPI 600 dpi 150 dpi 150 dpi
Resolution 4328 x 2979px 1024 x 768 1024 x 768

Characteristics

Audiovisual

File 1 File 2 File 3
Format MOV MOV MOV
Resolution 720 x 576px 1920 x 1080 640 x 480
FPS 25 24 29.97
Samplerate 48 kHz 48 kHz 44.1 kHz
Channels Stereo Surround 5.1 Mono

Data rate / Filesize

Type Duration Bitrate Filesize
Video 1 hour 210 Mb/s 92 GB
50 Mb/s 22 GB
25 Mb/s 11 GB
1,5 Mb/s 1 GB
Audio 1 hour 4,6 Mb/s 2 GB
128 kb/s 56 MB

Different Formats, different use cases

  • Preservation
  • Mezzanine
  • Access

Different Formats, different use cases

  • Preservation: Stand the test of time.
    Highest original quality.

  • Mezzanine: For daily work.
    High quality.

  • Access For quick and easy access.
    Quality not necessarily best/high.

Examples: Video

  • Preservation:

* Uncompressed * FFV1 * J2K-lossless * …

  • Mezzanine:

* ProRes * H.264 * DVCPRO50 * …

  • Access:

* MP4 * WebM * DVD * BluRay * …

Size (still) matters

Type Duration Bitrate Filesize Usage
Video 1 hour 210 Mb/s 92 GB Preservation
50 Mb/s 22 GB Preservation
25 Mb/s 11 GB Preservation / Mezzanine
1,5 Mb/s 1 GB Access
Audio 1 hour 4,6 Mb/s 2 GB Preservation
128 kb/s 56 MB Access

Data rate = Bitrate

  • Mbps / 8 = MB / second
  • MB/s * 60 = MB / minute
  • MB/min * 60 = MB / hour

Significant properties

  • Depends on media type.
  • Examples for A/V:
    • resolution
    • framerate
    • aspect ratio
    • colorspace
    • subsampling
    • …

More: FADGI Significant Properties for Digital Video - DRAFT

Significant properties

Image?

Significant properties

Audio?

Lossy, Lossless, Uncompressed?

How it affects quality and preservation.

Lossy

Zlad! Elektronik Supersonik

Generation Loss

Lossless

“It’s like ZIP for film!”

  • No generation loss
  • Way larger than lossy
  • Smaller than uncompressed

Uncompressed

Uncompressed - Think of it as:

1px RGB Image:

RRR GGG BBB AAA

1px YUV Image:

YYY UUU VVV

1 sample audio:

LLLLLLLL RRRRRRRR

Uncompressed Image

  • Width(px) x Height(px)
  • x Bits-Per-Pixel(bpp)
  • x FPS
  • / 8 = 1 second (in Byte)

Uncompressed Audio

  • Samplerate x bit-depth
  • x channels (even if silence!)
  • / 8 = 1 second (in Byte)

Default Formats

Film:

  • Image: DPX / TIFF files
  • Audio: PCM in WAV
  • Metadata: Mostly sidecar, some MD in image files.

Video:

  • Image: Default = lossy encoding
  • Audio: production = PCM, consumer = AAC
  • Metadata: Often embedded. Sometimes sidecar.

Best practices for A/V Formats

  • Capture analog video uncompressed (v210) or lossless (FFV1, J2K) to avoid adding digital generation loss.

  • Or as fallback option:
    At the highest quality (data rate) you can store and manage well over time.

  • Capture digital tape in its native format without generation loss (MiniDV, DAT, DigiBeta, etc.)

  • Store born-digital files “as original” as possible.

  • Audio preservation format is uncompressed WAV (PCM) for analog originals.

  • For video container formats, consider using MKV or MOV.
    MXF only for broadcast.

  • Choose formats that can be kept alive (=open & documented)

File formats and preservation implications

Complexity

Format Support

  • Popular?
  • Documented?
  • Well supported?
  • Can you handle/access it beyond shelf-life?

Obsolescence: Open vs Closed

Enigma encryption rotor windows

Theory vs Practice

Schematics

Error resilience

Containers

  • AVI: Audio Video Interleave
  • MOV: Quicktime
  • MKV: Matroska Video
  • MXF: Material eXchange Format
  • WAV / RIFF
  • MPG, MTS: MPEG Transport Stream

Video Codecs

  • H.264 (lossy, lossless, uncompressed)
  • H.265
  • MPEG-2 ( IMX, XDCAM )
  • ProRes
  • J2K (lossy, lossless)
  • FFV1 (lossless)
  • “Uncompressed”

Audio

  • AAC
  • MP3
  • Opus
  • PCM
  • FLAC

Risks to format longevity

  • Data errors
  • Obsolescence
  • Interoperability issues
  • Vendor lock-in

Countermeasures?

Comments?

Questions?