GiP-2.95-develop & list archives

[Vangelis forthnet]

On Thu Apr 7 12:09:34 BST 2016, artisticforge . wrote:

> I spent part of yesterday reading the list archives
> and have a better understanding now
> as to why GiP-2.95-dev is so slow.
> (snip)
> interesting reading the archives.

Hello terry :-)
(I do hope the pain relievers are still doing their job fine...)

 2.95-dev is indeed unsupported and undocumented,
plus it is under constant change - the best source to
read if you have time and want to get a clue as to how
things work in 2.95dev is to trace the individual commit
logs in the Github repo - start from
https://github.com/get-iplayer/get_iplayer/commit/8946c25446f38dea4baf9b4db813c8354e05a73e
in page 4 of main script commit history
https://github.com/get-iplayer/get_iplayer/commits/develop/get_iplayer?page=4
opening each commit in a separate tab
and reading the commit log (where available)
and work your way up to latest commit
https://github.com/get-iplayer/get_iplayer/commit/53e9c7f6f8635b1907609291ca20bbdd49e17978
in page 1:
https://github.com/get-iplayer/get_iplayer/commits/develop/get_iplayer

Then you'll get a good grasp of the features
removed/added during the development process...

> Part of that slowness is from perl
> doing a main part of the work.

2.95dev implements by default a native - pure perl -
HLS/DASH streamer; container change
(lossless remux) and transcoding, when specified,
is still being realised by FFmpeg.

 HLS modes for video and (re-introduced) DASH
modes for audio are now the default in latest snapshot.
FWIW, I do not find the native downloader to be
that much slower to FFmpeg...
FFmpeg itself cannot handle DASH downloads,
but if you'd like to re-assign FFmpeg to manage
HLS downloads (current - and only - behaviour
in GiP 2.94), you can do so via the --hls-ffmpeg switch.

> Nearly all downloads are hls
> with two to four times the bit rate.

You can get a glimpse of available modes/modesizes
for a specific pid via the --info (-i) switch.

perl get_iplayer-295dev-g53e9c7f6.pl --pid=b073rfc0 -i
=>
===================================================
modes:          original: 
flashhd1,flashvhigh1,flashvhigh2,flashhigh1,flashhigh2
,flashstd1,flashstd2,flashlow1,flashlow2,hlshd1,hlsvhigh1,hlshigh1,hlslow1,hlslo
w2,hvfhd1,hvfhd2,hvfsd1,hvfsd2,hvfvhigh1,hvfvhigh2,hvfhigh1,hvfhigh2,hvfstd1,hvf
std2,hvflow1,hvflow2,subtitles1

modesizes:      original: 
flashhd1=499MB,flashvhigh1=314MB,flashvhigh2=314MB,fla
shhigh1=168MB,flashhigh2=168MB,flashstd1=107MB,flashstd2=107MB,flashlow1=84MB,fl
ashlow2=84MB,hlshd1=510MB,hlsvhigh1=321MB,hlshigh1=171MB,hlslow1=109MB,hlslow2=1
09MB,hvfhd1=1182MB,hvfhd2=1182MB,hvfsd1=669MB,hvfsd2=669MB,hvfvhigh1=386MB,hvfvh
igh2=386MB,hvfhigh1=210MB,hvfhigh2=210MB,hvfstd1=121MB,hvfstd2=121MB,hvflow1=86M
B,hvflow2=86MB,subtitles1=60KB
===================================================

The flash* and hls* tvmodes are exactly the same
as you know them from GiP 2.94. If you'd like to
download one of those, indicate so via the --modes
(or --tvmode) switch.
The hvf* tvmodes are new to 2.95dev, they are the
"Video Factory" ones.
- hvfvhigh is comparable to hlsvhigh, but slightly better
both in resolution (540p) and BR (ca. 1700kbps).
- hvfsd is again 540p, but the doubled size is due to
50FPS, not to a mere increase of BR in the 25FPS file.
- hvfhd is 720p (same resolution as flashhd/hlshd),
but again the huge filesize is due to 50FPS.

 I am not following this currently, as I have
no interest in the 50FPS files, however it was
posted previously in the Support Forum
that the vast plethora of TV content on iplayer
is not 50FPS originally, so for most 50FPS files
there is a simple dublication of 25FPS=>50FPS,
IOW in a minute's worth of video stream, there
exist only 25 unique different frames.
 One notable exception to the above are sports
events (and possibly other genres where quick
motion is involved...).

Due to the excessive toll on bandwidth and
disk space storage, plus some issues pertaining to
1) older FFmpeg versions (<2.5), which do not
work with hvf streams,
2) the absence of AD versions in hvf format,
hls tvmodes are still the default for VOD.

Just some useful info for those trialing the dev version...

To you, terry, and all the rest,
take care!

Vangelis