[FFmpeg-user] "documented implicitly" part 2 [was: Re: Problem while converting DNG sequnece to video file]

Jim DeLaHunt list+ffmpeg-user at jdlh.com
Thu Aug 20 22:16:07 EEST 2020

On 2020-08-20 01:47, Paul B Mahol wrote:

> On 8/20/20, Michael Koch <astroelectronic at t-online.de> wrote:
>> Am 20.08.2020 um 10:29 schrieb Paul B Mahol:
>>> On 8/20/20, Michael Koch <astroelectronic at t-online.de> wrote:
>>>> …[snip]…
>>>> I think ffmpeg doesn't have a DNG decoder. Or it is completely
>>>> undocumented.
>>>> Searching for "DNG" in ffmpeg-all.html finds nothing.
>>> ffmpeg have DNG decoder.
>>> If you are unsure about something, better keep silence, instead of
>>> spreading incorrect information.
>> Why is such a useful feature not documented?
> Because DNG is not separate decoder but part of TIFF one.
> You could search trac tickets or commit logs, DNG was implemented as
> part of GSoC.

Another classic FFmpeg project statement. Let's put "search trac tickets 
or commit logs" in the FFmpeg documentation hall of fame, along with 
"documented implicitly".

Of _course_ FFmpeg supports DNG format. And of _course_ that is not 
stated in the mis-named documentation, "ffmpeg-all.html". Nor in the 
other documentation, `ffmpeg -formats`. Nor in the other other 
documentation, `ffmpeg --help demuxer=tiff_pipe`.

And of _course_ the person who says, with appropriate caution, 'I think 
ffmpeg doesn't have a DNG decoder. Or it is completely
undocumented.…' gets spanked for 'spreading incorrect information'.

And of _course_ there is no acknowledgement like, "gosh, FFmpeg 
documentation is pretty scattered, not surprising you didn't see this, 
if we had better documentation this would be easier".


% ffmpeg -hide_banner -formats
File formats:
  D. = Demuxing supported
  .E = Muxing supported
  D  3dostr          3DO STR
  DE dirac           raw Dirac
  DE dnxhd           raw DNxHD (SMPTE VC-3)
  D  tiertexseq      Tiertex Limited SEQ
  D  tiff_pipe       piped tiff sequence
  D  tmv             8088flex TMV

% ffmpeg -hide_banner --help demuxer=tiff_pipe
Demuxer tiff_pipe [piped tiff sequence]:
tiff demuxer AVOptions:
   -frame_size        <int>        .D........ force frame size in bytes (from 0 to INT_MAX) (default 0)
   -framerate         <video_rate> .D........ set the video framerate (default "25")
   -pixel_format      <string>     .D........ set video pixel format
   -video_size        <image_size> .D........ set video size
   -loop              <boolean>    .D........ force loop over input file sequence (default false)

[Note the absence of any mention of "DNG" in this documentation.]


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