[FFmpeg-devel] [PATCH]lavc/mlp_parse: Read wordlength from 0xba streams

[Carl Eugen Hoyos]

Am Fr., 14. Feb. 2020 um 01:26 Uhr schrieb Hendrik Leppkes
<h.leppkes at gmail.com>:
>
> On Fri, Feb 14, 2020 at 12:29 AM Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> >
> > Attached patch allows detecting s16 truehd streams encoded with
> > FFmpeg, only tested with FFmpeg's encoder, I did not look into any
> > specification.
>
> According to Dolbys Bitstream specification this read does not seem
> right. It reads half of a reserved field and 3 single-bit control
> fields - in a structure called "channel meaning", which otherwise only
> includes fields on channel assignment and interpretation, so this
> field being in there seems weird.
> Also, why would they code a literal value, and not a lookup table with
> fewer bits like the 0xbb case does?
>
> Unless we can find an actual real-world sample from a licensed encoder
> that can confirm the presence and accuracy of this field, I'm going to
> assume its not correct. It looks to me like it may be writing a MLP
> (ie. 0xbb) header, and not a TrueHD header - beyond the first
> differences, anyway. The high-level bitstream specification was not
> available when mlpenc.c was initially written.

Thank you for looking into this!
Is there a link to the high-level bitstream specification?

Carl Eugen