A few ffmpeg queries

[Vangelis forthnet]

 On Fri Sep 8 13:43:53 BST 2017, RS wrote:

> I realise you did not write the code but are only defending it

 Hi Richard; I wasn't "defending" the code,
I merely provided some additional info that
would explain your "for some reason" previous
comment:

>> get_iplayer for some reason uses a different format
>> for ffmpeg options depending on the value of
>> ! $opt->{ffmpegobsolete}

> As far as I am aware -loglevel is not a new ffmpeg option.

 Agreed; but it wasn't there from the start and its arguments
have changed over time; just browse:

https://github.com/get-iplayer/get_iplayer/blob/6dab3c86801d3ee2ce1d1a072c3471e945f04bf5/get_iplayer#L781-L799

 Also, I have an old patched version
of GiP 2.97 lying around (used for
flash modes), its help contains the entry:

> --ffmpeg-obsolete
> Indicates you are using an obsolete version of ffmpeg (<0.7)
> that does not support the -loglevel or -stats options,
> so --quiet, --verbose and --debug
> will not be applied to ffmpeg.

 To conclude ffmpegobsolete, that
setting also dictates the syntax used for
applying the bitstream audio filter during remux:

https://github.com/get-iplayer/get_iplayer/blob/6dab3c86801d3ee2ce1d1a072c3471e945f04bf5/get_iplayer#L7038-L7042

> v2.5 or above is needed for HLS
> and v3.0 or above is needed for DASH.

 HLS should be interpreted to actually mean
Video Factory HLS modes ("hvf", not the
"legacy" "hls" ones)

> (Does that leave any modes
> obsolete versions will work with?)

 "hls" will work OK, yielding tagged MP4 files;
dvf/hvf will produce (untagged) .TS files
(playable though by most SW/HW players
with support for h.264/aaclc codecs).

 I gather also daf (audio) modes would fail to
yield proper .m4a files; unsure about haf
modes, too...

Best regards,
Vangelis.