Results FFv1 and MKV study

  • Tech Blog

In 2013, meemoo chose MXF as a container and JPEG2000 as an encoding for our archive masters, together with content partners from the heritage sector.

The technological development of audiovisual codecs does not stand still and the development and possible standardisation of FFv1 and MKV are interesting evolutions.The codec is also lossless, but especially interesting because of the open source character of the formats and the wide range of tools available to manage the files. Think of open source encoders and decoders (ffmpeg), quality control software and players.

Meemoo recently completed a series of tests in which some technical characteristics of FFv1 and MKV were tried. The format emerges as a promising future format for audiovisual archive material. Through this study, meemoo gained insights in the practical usability of the new formats and questions to be further examined. The study was carried out together with Media Area and Packed vzw, and is part of the Preforma project, where meemoo is a member of the soundboard group.

During the study, a number of issues were measured which we state below. More details can be found in the accompanying report (in Dutch). First, we ascertained if the files could in fact be converted without loss of data from the current archive format (JPEG2000/MXF) to FFv1 in MKV. To do so, the frame-md5 of a file was measured post decoding of the source format (JPEG2000/MXF) and post decoding of the new format (FFv1/MKV). A lossless transcoding to the new format is perfectly possible: every decoded frame is identical, whatever the source. No data is lost in the converting process.

A number of technical characteristics of both codecs were also compared. We started with the compression rate and came to the conclusion that FFv1 video compresses almost as well as the existing meemoo archive master. There is a reduction of some percentages, but these can be explained by the more efficient audio codec (FLAC vs. PCM), rather than by differences between JPEG2000 and FFv1.

Finally, the performance of the decoding was measured to gain insight in the demands for capacity. The graph below shows the average transcoding speed for the entire set from the existing codec (in orange) and the new FFv1 standard (in blue). The transcoding speed is three to four times faster than the existing format. Note: there were no other libraries tested than open source ones for the decoding of the JPEG2000 files.

These tests give us a first insight and some practical experience with the new formats. This is of course only a first step and many questions remain unanswered, for example the hanging standardisation of the format (it is currently at the IETF for review), the support within our own MAM software for the format and the support for the export of fragments. In the course of this year, meemoo will follow up on the developments within the Preforma and Cellar workgroup and do further tests.

The script used to convert the files from the existing codec to FFv1 in MKV are available in open source and can be found here: https://github.com/viaacode/jp2k-ffv1/

A link to the report of Media Area can be found here.

Matthias Priem

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