File Format Considerations

The Goal

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

Data Structure

Digital Video Trinity

Remember?

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

Generation Loss

Here's an example where one can see the difference between each encoded version in popular broadcast codecs.

Since it's almost certain that there's not "evergreen format", any format will sooner or later have to be migrated to another one. The longer an item is preserved, the more often it will encour such a format change (transcoding). Therefore, generation loss should be considered.

Also: Usage of archive material: What happens if you hand out your material to an editor, say on DVD or a mezzanine format? The editor then edits and exports to another format, the broadcaster or cinema then to another? ...and in the end this work is then also converted to an access format.

And theeeen, years later that access copy is used as a source for a documentary or online edit.

How many generation losses accumulate here? How could they be reduced?

Generally: please try to avoid unnecessary generation losses. Why not? :)

Lossless

"It's like ZIP for film!"

No generation loss
Way larger than lossy
Smaller than uncompressed

Uncompressed

No generation loss
Dead simple (=preserves well)
The largest possible version
There's more than just 1 "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

Theory vs Practice

Schematics

Error resilience

Popular formats

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

Topic 1 - Digital Files

File Format Considerations

The Goal

Data Structure

Digital Video Trinity

Remember?

Characteristics

Image

Characteristics

Audiovisual

Data rate / Filesize

Different Formats, different use cases

Different Formats, different use cases

Examples: Video

Size (still) matters

Data rate = Bitrate

Significant properties

Significant properties

Image?

Significant properties

Audio?

Lossy, Lossless, Uncompressed?

Lossy

Generation Loss

Lossless

Uncompressed

Uncompressed - Think of it as:

Uncompressed Image

Uncompressed Audio

Default Formats

Best practices for A/V Formats

File formats and preservation implications

Complexity

Format Support

Obsolescence: Open vs Closed

Theory vs Practice

Schematics

Error resilience

Popular formats

Containers

Video Codecs

Audio

Risks to format longevity

Comments?

Questions?

Links