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problem with limitng output bitrate and VBV underflow warning

negin tebyani
I am using this commad to transcode a video with 12000k bitrate to a lower
bitrate like 300k.

here is my command:

ffmpeg -i 12000.mp4 -movflags faststart -c:v libx264 -x264opts
'keyint=288:min-keyint=24:8x8dct:sliced-threads=0' -deblock 1:1 -flags
+loop -b:v 300k -maxrate 300k -bufsize 1000k -tune psnr  -vf
"scale=-1280:720:flags=spline+full_chroma_inp+full_chroma_int+accurate_rnd+bitexact"
-acodec libfdk_aac -b:a 320k -coder 1 -me_range 16 -sc_threshold 42 -bf 10
-q:v 1 -qmin 0 -qmax 35 -trellis 2 -mbtree 1 -mixed-refs 1 -preset veryslow
video.mp4

I need the bitrate to be 2000, but after using this command and using media
info, I see that bitrate is different from what I specified (2000 for
ecample) and there is a nominal bitrate which is what I specified in my
command.

and during the convert process i get the VBV underflow warning after a
short time passes. until that warning hasn't showed up, the bitrate seems
to be fine. but after that the bitrate starts to get higher.

here is my console output:

[libx264 @ 0x20bb0c0] VBV underflow (frame 2992, -20064 bits)
[libx264 @ 0x20bb0c0] VBV underflow (frame 2993, -13888 bits)
[libx264 @ 0x20bb0c0] VBV underflow (frame 2995, -520 bits)
[libx264 @ 0x20bb0c0] VBV underflow (frame 2996, -992 bits)
[libx264 @ 0x20bb0c0] VBV underflow (frame 2997, -1320 bits)
[libx264 @ 0x20bb0c0] VBV underflow (frame 2998, -9528 bits)
[libx264 @ 0x20bb0c0] VBV underflow (frame 2999, -744 bits)
[mp4 @ 0x20ba1e0] Starting second pass: moving the moov atom to the
beginning of the file
frame= 3000 fps= 13 q=-1.0 Lsize=   18665kB time=00:01:00.01
bitrate=2547.9kbits/s
video:16252kB audio:2346kB subtitle:0kB other streams:0kB global
headers:0kB muxing overhead: 0.363480%
[libx264 @ 0x20bb0c0] frame I:15    Avg QP:30.80  size: 46683
[libx264 @ 0x20bb0c0] frame P:592   Avg QP:31.14  size: 16537
[libx264 @ 0x20bb0c0] frame B:2393  Avg QP:34.69  size:  2570
[libx264 @ 0x20bb0c0] consecutive B-frames:  0.8%  3.3%  5.4%  9.6%  3.3%
76.2%  0.7%  0.0%  0.6%  0.0%  0.0%
[libx264 @ 0x20bb0c0] mb I  I16..4: 37.0% 48.8% 14.2%
[libx264 @ 0x20bb0c0] mb P  I16..4:  9.1%  9.4%  1.0%  P16..4: 24.2%  7.5%
 5.7%  0.8%  0.1%    skip:42.2%
[libx264 @ 0x20bb0c0] mb B  I16..4:  0.4%  0.2%  0.0%  B16..8: 17.9%  4.2%
 0.7%  direct: 0.9%  skip:75.6%  L0:37.7% L1:49.0% BI:13.3%
[libx264 @ 0x20bb0c0] 8x8 transform intra:46.4% inter:49.8%
[libx264 @ 0x20bb0c0] direct mvs  spatial:99.9% temporal:0.1%
[libx264 @ 0x20bb0c0] coded y,uvDC,uvAC intra: 18.8% 27.9% 7.3% inter: 5.6%
3.5% 0.3%
[libx264 @ 0x20bb0c0] i16 v,h,dc,p: 29% 46% 10% 15%
[libx264 @ 0x20bb0c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11% 19% 55%  3%  2%
 3%  3%  2%  3%
[libx264 @ 0x20bb0c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 30% 17%  3%  5%
 6%  5%  4%  4%
[libx264 @ 0x20bb0c0] i8c dc,h,v,p: 65% 20%  8%  6%
[libx264 @ 0x20bb0c0] Weighted P-Frames: Y:5.6% UV:4.6%
[libx264 @ 0x20bb0c0] ref P L0: 57.1% 15.8% 13.9%  3.3%  2.4%  1.7%  1.3%
 0.6%  0.6%  0.8%  0.5%  0.4%  0.4%  0.4%  0.4%  0.3%
[libx264 @ 0x20bb0c0] ref B L0: 84.1%  9.0%  2.3%  1.4%  0.6%  0.6%  0.6%
 0.2%  0.2%  0.3%  0.2%  0.2%  0.1%  0.1%  0.1%
[libx264 @ 0x20bb0c0] ref B L1: 96.4%  3.6%
[libx264 @ 0x20bb0c0] kb/s:2218.78


and here is a demo of video:

https://streamable.com/e6dbg
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Re: problem with limitng output bitrate and VBV underflow warning

negin tebyani
forgot to show mediainfo output:

General
Complete name                            : 300from12000.mp4
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom
File size                                : 18.2 MiB
Duration                                 : 1mn 0s
Overall bit rate                         : 2 547 Kbps
Writing application                      : Lavf56.25.101

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L5.0
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 16 frames
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1mn 0s
Bit rate                                 : 2 219 Kbps
Nominal bit rate                         : 300 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 50.000 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.048
Stream size                              : 15.9 MiB (87%)
Writing library                          : x264 core 142 r2495 6a301b6
Encoding settings                        : cabac=1 / ref=16 / deblock=1:1:1
/ analyse=0x3:0x133 / me=umh / subme=10 / psy=0 / mixed_ref=1 / me_range=16
/ chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 /
fast_pskip=1 / chroma_qp_offset=0 / threads=4 / lookahead_threads=1 /
sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 /
constrained_intra=0 / bframes=10 / b_pyramid=2 / b_adapt=2 / b_bias=0 /
direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=288 / keyint_min=24
/ scenecut=42 / intra_refresh=0 / rc_lookahead=60 / rc=cbr / mbtree=1 /
bitrate=300 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=35 / qpstep=4 /
vbv_maxrate=300 / vbv_bufsize=1000 / nal_hrd=none / filler=0 /
ip_ratio=1.40 / aq=1:0.00
Language                                 : English

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 1mn 0s
Duration_LastFrame                       : -11ms
Bit rate mode                            : Constant
Bit rate                                 : 320 Kbps
Channel count                            : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Delay relative to video                  : 40ms
Stream size                              : 2.29 MiB (13%)
Language                                 : English


On Sun, Apr 9, 2017 at 12:56 PM, negin tebyani <[hidden email]>
wrote:

> I am using this commad to transcode a video with 12000k bitrate to a lower
> bitrate like 300k.
>
> here is my command:
>
> ffmpeg -i 12000.mp4 -movflags faststart -c:v libx264 -x264opts
> 'keyint=288:min-keyint=24:8x8dct:sliced-threads=0' -deblock 1:1 -flags
> +loop -b:v 300k -maxrate 300k -bufsize 1000k -tune psnr  -vf
> "scale=-1280:720:flags=spline+full_chroma_inp+full_chroma_int+accurate_rnd+bitexact"
> -acodec libfdk_aac -b:a 320k -coder 1 -me_range 16 -sc_threshold 42 -bf 10
> -q:v 1 -qmin 0 -qmax 35 -trellis 2 -mbtree 1 -mixed-refs 1 -preset veryslow
> video.mp4
>
> I need the bitrate to be 2000, but after using this command and using
> media info, I see that bitrate is different from what I specified (2000 for
> ecample) and there is a nominal bitrate which is what I specified in my
> command.
>
> and during the convert process i get the VBV underflow warning after a
> short time passes. until that warning hasn't showed up, the bitrate seems
> to be fine. but after that the bitrate starts to get higher.
>
> here is my console output:
>
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2992, -20064 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2993, -13888 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2995, -520 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2996, -992 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2997, -1320 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2998, -9528 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2999, -744 bits)
> [mp4 @ 0x20ba1e0] Starting second pass: moving the moov atom to the
> beginning of the file
> frame= 3000 fps= 13 q=-1.0 Lsize=   18665kB time=00:01:00.01
> bitrate=2547.9kbits/s
> video:16252kB audio:2346kB subtitle:0kB other streams:0kB global
> headers:0kB muxing overhead: 0.363480%
> [libx264 @ 0x20bb0c0] frame I:15    Avg QP:30.80  size: 46683
> [libx264 @ 0x20bb0c0] frame P:592   Avg QP:31.14  size: 16537
> [libx264 @ 0x20bb0c0] frame B:2393  Avg QP:34.69  size:  2570
> [libx264 @ 0x20bb0c0] consecutive B-frames:  0.8%  3.3%  5.4%  9.6%  3.3%
> 76.2%  0.7%  0.0%  0.6%  0.0%  0.0%
> [libx264 @ 0x20bb0c0] mb I  I16..4: 37.0% 48.8% 14.2%
> [libx264 @ 0x20bb0c0] mb P  I16..4:  9.1%  9.4%  1.0%  P16..4: 24.2%  7.5%
>  5.7%  0.8%  0.1%    skip:42.2%
> [libx264 @ 0x20bb0c0] mb B  I16..4:  0.4%  0.2%  0.0%  B16..8: 17.9%  4.2%
>  0.7%  direct: 0.9%  skip:75.6%  L0:37.7% L1:49.0% BI:13.3%
> [libx264 @ 0x20bb0c0] 8x8 transform intra:46.4% inter:49.8%
> [libx264 @ 0x20bb0c0] direct mvs  spatial:99.9% temporal:0.1%
> [libx264 @ 0x20bb0c0] coded y,uvDC,uvAC intra: 18.8% 27.9% 7.3% inter:
> 5.6% 3.5% 0.3%
> [libx264 @ 0x20bb0c0] i16 v,h,dc,p: 29% 46% 10% 15%
> [libx264 @ 0x20bb0c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 11% 19% 55%  3%  2%
>  3%  3%  2%  3%
> [libx264 @ 0x20bb0c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 30% 17%  3%  5%
>  6%  5%  4%  4%
> [libx264 @ 0x20bb0c0] i8c dc,h,v,p: 65% 20%  8%  6%
> [libx264 @ 0x20bb0c0] Weighted P-Frames: Y:5.6% UV:4.6%
> [libx264 @ 0x20bb0c0] ref P L0: 57.1% 15.8% 13.9%  3.3%  2.4%  1.7%  1.3%
>  0.6%  0.6%  0.8%  0.5%  0.4%  0.4%  0.4%  0.4%  0.3%
> [libx264 @ 0x20bb0c0] ref B L0: 84.1%  9.0%  2.3%  1.4%  0.6%  0.6%  0.6%
>  0.2%  0.2%  0.3%  0.2%  0.2%  0.1%  0.1%  0.1%
> [libx264 @ 0x20bb0c0] ref B L1: 96.4%  3.6%
> [libx264 @ 0x20bb0c0] kb/s:2218.78
>
>
> and here is a demo of video:
>
> https://streamable.com/e6dbg
>
>
>
>
>
>
>
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Re: problem with limitng output bitrate and VBV underflow warning

Moritz Barsnick
In reply to this post by negin tebyani
On Sun, Apr 09, 2017 at 12:56:01 +0430, negin tebyani wrote:

> I am using this commad to transcode a video with 12000k bitrate to a lower
> bitrate like 300k.
>
> here is my command:
>
> ffmpeg -i 12000.mp4 -movflags faststart -c:v libx264 -x264opts
> 'keyint=288:min-keyint=24:8x8dct:sliced-threads=0' -deblock 1:1 -flags
> +loop -b:v 300k -maxrate 300k -bufsize 1000k -tune psnr  -vf
> "scale=-1280:720:flags=spline+full_chroma_inp+full_chroma_int+accurate_rnd+bitexact"
> -acodec libfdk_aac -b:a 320k -coder 1 -me_range 16 -sc_threshold 42 -bf 10
> -q:v 1 -qmin 0 -qmax 35 -trellis 2 -mbtree 1 -mixed-refs 1 -preset veryslow
> video.mp4
[...]

> here is my console output:
>
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2992, -20064 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2993, -13888 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2995, -520 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2996, -992 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2997, -1320 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2998, -9528 bits)
> [libx264 @ 0x20bb0c0] VBV underflow (frame 2999, -744 bits)
> [mp4 @ 0x20ba1e0] Starting second pass: moving the moov atom to the
> beginning of the file
> frame= 3000 fps= 13 q=-1.0 Lsize=   18665kB time=00:01:00.01
> bitrate=2547.9kbits/s

negin, on this list you are kindly asked to provide the actual command
line you are using, along with the complete, uncut console output. In
your e-mail, you are omitting important information.

Furthermore, I can see (guess!) that you are using a rather old version
of ffmpeg. (I would know for sure if you had provided the complete
console output.) We also kindly ask you to try with the latest version
first, before reporting. If you can't build for yourself, you can find
binaries built from git master both for Linux
(http://johnvansickle.com/ffmpeg/) and Windows
(https://www.johnvansickle.com/ffmpeg/). Choose "git", not "release".

> I need the bitrate to be 2000, but after using this command and using media
> info, I see that bitrate is different from what I specified (2000 for
> ecample) and there is a nominal bitrate which is what I specified in my
> command.

The mediainfo output you provided in the other e-mail is for a 300k
encoding, not a 2000k encoding. Please don't mix up cases! Output from
ffprobe instead of mediainfo should be just fine, BTW, unless mediainfo
is telling you something ffprobe isn't.

> [libx264 @ 0x20bb0c0] VBV underflow (frame 2992, -20064 bits)

I don't know anything about this though. ;-)

> https://streamable.com/e6dbg

Which is totally different (and thereby irrelevant), because that site
apparently re-encodes your uploaded video. Mixing up all these things
is making it really difficult to understand the actual issue.

Moritz
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Re: problem with limitng output bitrate and VBV underflow warning

James Darnley
In reply to this post by negin tebyani
On 2017-04-09 10:26, negin tebyani wrote:
> -qmax 35

And you wonder why the encoder can't lower quality enough to stay within
the buffer you set?



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Re: problem with limitng output bitrate and VBV underflow warning

negin tebyani
>
>
> And you wonder why the encoder can't lower quality enough to stay within
> the buffer you set?
>

I set this to 69 and the problem is solved. thanks
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