[FFmpeg-user] Metadata text length

Marton Balint cus at passwd.hu
Tue Mar 19 03:40:11 EET 2019

On Mon, 18 Mar 2019, Richard F via ffmpeg-user wrote:

> On 18/03/2019 20:25, Moritz Barsnick wrote:
>> On Mon, Mar 18, 2019 at 19:40:41 +0000, FFmpeg user discussions wrote:
>>> I think the patch here: https://patchwork.ffmpeg.org/patch/12047 has
>>> introduced a limit to the length of plain ASCII text that can be written
>>> into mpegts metadata fields. I'm seeing ffmpeg exit when trying to write
>>> a string of more than ~150 characters with "Too long service or provider
>>> name".
>> You should show us your actual command line and its complete, uncut
>> console output.
> This is the 2nd stage of a 2 stage conversion, the last stage concats
> intermediate files when needed, manipulates stream order and adds
> metadata for several formats when required (hence a lot of unnecessary
> metadata for ts or m2ts formats - but same result).
> Removing the excess metadata makes no difference, the code takes the
> long "title" string and tries to put it into "service name" by my
> reading.  ~150 char seems to be the limit (previously didn't hit a
> limit).  The long Title and other tags are used in other formats like
> mkv and m4a podcasts.
> Obvious workaround - I just want to know what number to truncate to, it
> seems rather less than 254, without UTF chars.

254 bytes are the limit for UTF8, 255 for ASCII. And only the "title" 
metadata is affected as the mpegts muxer is using that for service name if 
no "service_name" metadata is given. So alternatively you can specify a 
"service_name" metadata field so the "title" metadata won't be 
misinterpreted as service name.

The old code created broken SDT with long service or provider names by 
the way...


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