convert images to a video (Ubuntu)

use =avconv= package

e.g.  to convert images (v_1.png, v_2.png ...) to 'velocity.mp4'

>>> avconv -i v_%d.png -b:v 1000k velocity.mp4

- i :: input file
- b :: bitrate

What bitrate should I use when encoding my video?

File size = bitrate (kilobits per second) x duration

Output size	Bitrate	Filesize
320x240 pixels	400 kbps	3MB / minute
480x270 pixels	700 kbps	5MB / minute
1024 x 576 pixels	1500 kbps	11MB / minute
1280x720 pixels	2500 kbps	19MB / minute
1920x1080 pixels	4000 kbps	30MB / minute

kbps= Kilo Bits Per Second

log

$ avconv -i t_%d.png -b:v 2500k temperature.mp4
ffmpeg version 2.8.15-0ubuntu0.16.04.1 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
Input #0, image2, from 't_%d.png':
  Duration: 00:00:04.04, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: png, rgb24(pc), 1022x837, 25 fps, 25 tbr, 25 tbn, 25 tbc
No pixel format specified, yuv444p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
[libx264 @ 0xf47d80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0xf47d80] profile High 4:4:4 Predictive, level 3.1, 4:4:4 8-bit
[libx264 @ 0xf47d80] 264 - core 148 r2643 5c65704 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 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=4 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=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=2500 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'temperature.mp4':
  Metadata:
    encoder         : Lavf56.40.101
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv444p, 1022x837, q=-1--1, 2500 kb/s, 25 fps, 12800 tbn, 25 tbc
    Metadata:
      encoder         : Lavc56.60.100 libx264
Stream mapping:
  Stream #0:0 -> #0:0 (png (native) -> h264 (libx264))
Press [q] to stop, [?] for help
Input stream #0:0 frame changed from size:1022x837 fmt:rgb24 to size:1009x837 fmt:rgb24
Input stream #0:0 frame changed from size:1009x837 fmt:rgb24 to size:1022x837 fmt:rgb24
frame=  101 fps=0.0 q=-1.0 Lsize=    1228kB time=00:00:03.96 bitrate=2539.7kbits/s    
video:1226kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.161340%
[libx264 @ 0xf47d80] frame I:1     Avg QP:22.02  size:  6166
[libx264 @ 0xf47d80] frame P:39    Avg QP: 6.78  size: 13587
[libx264 @ 0xf47d80] frame B:61    Avg QP: 8.27  size: 11776
[libx264 @ 0xf47d80] consecutive B-frames: 16.8%  5.9%  5.9% 71.3%
[libx264 @ 0xf47d80] mb I  I16..4:  8.1% 88.1%  3.9%
[libx264 @ 0xf47d80] mb P  I16..4:  4.4%  2.9%  3.7%  P16..4:  2.5%  1.0%  1.0%  0.0%  0.0%    skip:84.5%
[libx264 @ 0xf47d80] mb B  I16..4:  2.8%  1.1%  2.3%  B16..8:  2.9%  1.3%  1.0%  direct: 0.6%  skip:88.0%  L0:47.8% L1:37.6% BI:14.6%
[libx264 @ 0xf47d80] final ratefactor: 7.45
[libx264 @ 0xf47d80] 8x8 transform intra:29.6% inter:33.6%
[libx264 @ 0xf47d80] coded y,u,v intra: 36.5% 23.7% 20.0% inter: 2.6% 0.9% 0.8%
[libx264 @ 0xf47d80] i16 v,h,dc,p: 93%  4%  3%  0%
[libx264 @ 0xf47d80] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 20%  7% 55%  3%  3%  2%  4%  2%  4%
[libx264 @ 0xf47d80] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 14% 20% 15%  6% 10%  6% 12%  6% 11%
[libx264 @ 0xf47d80] Weighted P-Frames: Y:51.3% UV:7.7%
[libx264 @ 0xf47d80] ref P L0: 55.5%  5.7% 19.9% 12.8%  6.1%
[libx264 @ 0xf47d80] ref B L0: 74.3% 19.9%  5.8%
[libx264 @ 0xf47d80] ref B L1: 93.3%  6.7%
[libx264 @ 0xf47d80] kb/s:2483.97

References:

https://stackoverflow.com/questions/16315192/avconv-make-a-video-from-a-subset-on-images

https://libav.org/avconv.html

https://www.ezs3.com/public/What_bitrate_should_I_use_when_encoding_my_video_How_do_I_optimize_my_video_for_the_web.cfm