[FFmpeg-user] Faster ffprobe-based detection of open GOP h264 ?

[Andrew Randrianasulu]

I was looking at videohelp forum

https://web.archive.org/web/20201125203546/https://forum.videohelp.com/threads/398119-Cutting-Open-GOP-H264-videos-properly

(web archive link because it hopefully will stay active for some time even
if forum software will be upgraded and ruin old links in the future)

It provides this ffprobe-based method of seeing if given h264 video stream
is Open GOP or not :

echo entry,pkt_pts_time,pict_type,coded_picture_number > "%~n1.csv"

ffprobe -v 32 -stats -y -hide_banner -i %1 -select_streams v -print_format
csv -of csv  -show_entries
"frame=pkt_pts_time,pict_type,coded_picture_number" >> "%~n1.csv"

=== quote ====

You can see that the last frame of the first GOP is a B frame -- so that's
an open GOP. Also, the coded picture number is higher than that of the I
frame after it -- indicating that the I frame had to be decoded before the
B frame, another indication of an open GOP.

=== quote ends ===

I checked one of my videos:

ffprobe -v 32 -stats -y -hide_banner -i
~/Sea_of_life_plus_Mikura_dolphins_test.mp4 -select_streams v -print_format
csv -of csv  -show_entries
"frame=pkt_pts_time,pict_type,coded_picture_number" >> "Sea_of_life-n1.csv"

and it seems resulting cvs file show it as open GOP consistently with
mediainfo:

frame,8.308300,B,250
frame,8.341667,I,249
frame,8.375033,B,253

mediainfo (v23.11) snip:

=== snip ===

Video

ID                                       : 1

Format                                   : AVC
          Format/Info                              : Advanced Video Codec

 Format profile                           : High at L4.1
Format settings                          : 4 Ref Frames

Format settings, CABAC                   : No
Format settings, Reference frames        : 4 frames

 Codec ID                                 : avc1

Codec ID/Info                            : Advanced Video Coding

 Duration                                 : 5 min 4 s
Bit rate                                 : 16.0 Mb/s
Width                                    : 1 920 pixels

Height                                   : 1 080 pixels

Display aspect ratio                     : 16:9

Frame rate mode                          : Constant

Frame rate                               : 29.970 (30000/1001) FPS
Color space                              : YUV

Chroma subsampling                       : 4:2:0

Bit depth                                : 8 bits

Scan type                                : Progressive

 Bits/(Pixel*Frame)                       : 0.257
Stream size                              : 575 MiB (99%)

Writing library                          : x264 core 148

Encoding settings                        : cabac=0 / ref=3 / deblock=1:0:0
/ analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 /
mixed_ref=1 / me_range=16 / chroma_me=0 / trellis=1 / 8x8dct=1 / cqm=0 /
deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=3 /
lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 /
bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=0
/ b_bias=0 / direct=1 / weightb=1 / open_gop=1 / weightp=2 / keyint=250 /
keyint_min=25 / scenecut=0 / intra_refresh=0 / rc_lookahead=40 / rc=abr /
mbtree=1 / bitrate=16000 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 /
qpstep=4 / ip_ratio=1.41 / aq=1:1.00

Codec configuration box                  : avcC

==== snip ends ===

So,  at least I may try to cut this video at various intervals and see if
cutting breaks on specifically open-gop h264 stream.

But as  it was said in forum post above - ffprobe  a bit slow, few minutes
for whole video, eating one cpu core completely.

Is there faster way to get this info ?