[FFmpeg-user] 3D SBS with ffmpeg quality question

[Moritz Barsnick]

Hi Sully,

> I am trying to come up with a reliable method to burn my 3D BluRays
> to disk as

Are you burning, as in "creating an optical disc", or are you ripping,
as in "writing the BluRay disk's content to a file on harddisk"?

On Wed, May 23, 2018 at 22:07:06 -0400, Sully Beck wrote:
> I'm not sure why you say that this cannot be correct.  I promise that 
> the above command is EXACTLY what I typed.

Yes, but it is not exactly what the frame rate is. Have you even
compared the output of your mediainfo commands?

-Frame rate                               : 23.976 (24000/1001) FPS
+Frame rate                               : 23.976 (23976/1000) FPS

The latter is from ffmpeg. You should have told ffmpeg to use
"24000/1001", to be precise. It may or may not matter for your player
though.

> I do mean that the quality of the encoded file (ffmpeg) is inferior to 
> the PavTube version.

Did you notice that you did "imitate" some of the details of the
PavTube encoding, but not all? If, again, you compared your outputs,
you would have noticed differences such as:

 Format/Info                              : Advanced Video Codec
-Format profile                           : Baseline at L4.1
+Format profile                           : High at L4.1
 Format settings, CABAC                   : No
-Format settings, ReFrames                : 1 frame
+Format settings, ReFrames                : 4 frames
 Codec ID                                 : avc1

and especially:

-Writing library                          : x264 core 148
-Encoding settings                        : cabac=0 / ref=1 /
-deblock=1:0:0 / analyse=0x1:0x111 / me=dia / subme=7 / psy=1 /
-psy_rd=1.00:0.00 / mixed_ref=0 / me_range=4 / chroma_me=1 / trellis=0 /
-8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 /
-threads=1 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 /
-interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=0 /
-weightp=0 / keyint=12 / keyint_min=7 / scenecut=40 / intra_refresh=0 /
-rc_lookahead=12 / rc=abr / mbtree=1 / bitrate=15000 / ratetol=1.0 /
-qcomp=0.60 / qpmin=3 / qpmax=51 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
-Language                                 : English
+Writing library                          : x264 core 152
+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=1 / trellis=1 /
+8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 /
+threads=24 / lookahead_threads=4 / sliced_threads=0 / nr=0 / decimate=1
+/ interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 /
+b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 /
+weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 /
+rc_lookahead=40 / rc=abr / mbtree=1 / bitrate=15000 / ratetol=1.0 /
+qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00

Since PavTube uses libx264, you may have a chance of duplicating its
results if you use those exact setting for x264. I don't know if you
can hit them with an ffmpeg combination of "-preset" and bandwidth (and
"-crf") options, or you have to duplicate them through the "x264opts"
and "x264-params" options. But that's worth a try, unless someone
figures out from looking at this why it yields worde results.

I'm confused that ffmpeg's options seem to be trying harder to get a
good quality/bandwidth ratio, but don't succeed according to your
observation. But I'm no expert.

Good luck,
Moritz