[flac-dev] max size for album art?

Timothy B. Terriberry tterribe at xiph.org
Wed May 10 21:12:37 UTC 2017

lvqcl wrote:
> Scott Brown <scottcbrown at gmail.com> wrote:
>> Is there any size limitation for album art?
> Slightly less than 16 megabytes.

Not directly related to FLAC, but tangentially related, since FLAC is 
sometimes converted to Opus with tags imported, but as documented at the 
bottom of the page here: <https://tools.ietf.org/html/rfc7845#page-24>, 
Opus allows implementations to ignore any metadata (which includes 
BASE64-encoded album art) after one Ogg page's worth.

That gives a practical limitation of a bit over 47 kB for all album art 
(before BASE64 encoding), if you would like it to work everywhere. This 
was done to avoid the need for an unbounded buffer in embedded 
applications, such as Rockbox. Or, more accurately, the Rockbox 
implementation was already ignoring tags beyond that point, and the RFC 
just documented that behavior. I would not be surprised to find that 
embedded FLAC implementations have similar limits that are much smaller 
than 16 MB, but I don't know if those are spelled out anywhere.

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