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• During transcoding, does output quality of a video improve when i give output bitrate more than input video's bitrate ?

  19 septembre 2013, par Jobin Jose

  I use ffmpeg for converting videos.
  As i understand, the bitrate of a video stream is the number of bits which constitute the video over 1 second of time.
  What happens when i specify the output video bitrate to be more than the input video's bitrate ?
  For example :
  If bitrate of "Input.mp4" is 2000KBps and i want to convert it to "Output.mp4" with output bitrate set to 3000KBps.
  How will the converter create the extra 1000 bits(3000-2000) for every second of video ?

• ffmpeg : convert audio-only flv to swf

  5 octobre 2011, par Michael Brewer-Davis

  My Flex application records audio-only FLV files using red5—I'd like to convert these to SWF files so I can embed them in other SWF files. (I could also convert to MP3 and then embed them into SWFs myself, but I'd prefer a one step solution.)

  Anyone have experience doing this ?

  What I've tried :

  The following naive ffmpeg command fails :

  > ffmpeg -i 3139747641.flv -vn movie.swf
  
  FFmpeg version SVN-r21751-snapshot, Copyright (c) 2000-2010 Fabrice Bellard, et al.
  
    built on Feb 11 2010 09:15:42 with gcc 4.2.1 (SUSE Linux)
  
    configuration: --enable-gpl --enable-nonfree
  
    libavutil     50. 9. 0 / 50. 9. 0
  
    libavcodec    52.53. 0 / 52.53. 0
  
    libavformat   52.52. 0 / 52.52. 0
  
    libavdevice   52. 2. 0 / 52. 2. 0
  
    libswscale     0.10. 0 /  0.10. 0
  
  [flv @ 0x8a5e3a0]Could not find codec parameters (Video: 0x0000)
  
  [flv @ 0x8a5e3a0]Estimating duration from bitrate, this may be inaccurate
  
  Input #0, flv, from '3139747641.flv':
  
    Metadata:
  
      audiocodecid    : -1
  
      duration        : 0
  
      videocodecid    : -1
  
      canSeekToEnd    : true
  
    Duration: 00:00:14.88, start: 0.000000, bitrate: N/A
  
      Stream #0.0: Video: 0x0000, 1k tbr, 1k tbn, 1k tbc
  
      Stream #0.1: Audio: nellymoser, 8000 Hz, mono, s16
  
  Output #0, swf, to 'movie.swf':
  
      Stream #0.0: Audio: 0x0000, 8000 Hz, mono, s16, 64 kb/s
  
  Stream mapping:
  
    Stream #0.1 -> #0.0
  
  Encoder (codec id 86017) not found for output stream #0.0

  I've tried adding a dummy video, but this also failed :

  > ffmpeg -i dummy.mov -i 3139747641.flv movie.swf
  
      
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'dummy.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 512
  
      compatible_brands: qt  
  
      encoder         : Lavf52.52.0
  
      encoder-eng     : Lavf52.52.0
  
    Duration: 00:00:00.10, start: 0.000000, bitrate: 62 kb/s
  
      Stream #0.0(eng): Video: mpeg4, yuv420p, 10x10 [PAR 1:1 DAR 1:1], 1 kb/s, 10 fps, 10 tbr, 10 tbn, 10 tbc
  
  [flv @ 0x8a67fa0]Could not find codec parameters (Video: 0x0000)
  
  [flv @ 0x8a67fa0]Estimating duration from bitrate, this may be inaccurate
  
  Input #1, flv, from '3139747641.flv':
  
    Metadata:
  
      audiocodecid    : -1
  
      duration        : 0
  
      videocodecid    : -1
  
      canSeekToEnd    : true
  
    Duration: 00:00:14.88, start: 0.000000, bitrate: N/A
  
      Stream #1.0: Video: 0x0000, 1k tbr, 1k tbn, 1k tbc
  
      Stream #1.1: Audio: nellymoser, 8000 Hz, mono, s16
  
  picture size invalid (0x0)
  
  Cannot allocate temp picture, check pix fmt

• Add SRT subtitle to video with ffmpeg

  3 juillet 2015, par jAckOdE

  I use ffmpeg to encode, and add subtitle to a video by following command

  $ ffmpeg -i hifi.avi -i hifi.srt -acodec libfaac -ar 48000 -ab 128k -ac 2 -vcodec libx264 -vpre ipod640 -s 480x240 -b 256k -scodec copy  hifi.m4v -newsubtitle

  Here is the output

  ffmpeg version 0.8.git, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Aug  4 2011 11:11:39 with gcc 4.5.2
  
    configuration: --extra-cflags=-I/usr/local/include --extra-ldflags=-L/usr/local/lib --disable-shared --enable-static --enable-gpl --enable-postproc --enable-pthreads --enable-ffplay --disable-ffserver --enable-memalign-hack --enable-nonfree --enable-libfaac --arch=x86 --enable-swscale --enable-libx264 --enable-avfilter --enable-debug=3
  
    libavutil    51. 11. 1 / 51. 11. 1
  
    libavcodec   53.  9. 1 / 53.  9. 1
  
    libavformat  53.  6. 0 / 53.  6. 0
  
    libavdevice  53.  2. 0 / 53.  2. 0
  
    libavfilter   2. 27. 5 /  2. 27. 5
  
    libswscale    2.  0. 0 /  2.  0. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  Input #0, avi, from 'hifi.avi':
  
    Metadata:
  
      encoder         : VirtualDubMod 1.5.4.1 (build 2178/release)
  
      IAS1            : English
  
    Duration: 01:49:02.20, start: 0.000000, bitrate: 897 kb/s
  
      Stream #0.0: Video: mpeg4 (Simple Profile), yuv420p, 544x304 [SAR 1:1 DAR 34:19], 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: mp3, 48000 Hz, stereo, s16, 32 kb/s
  
  [srt @ 0152c100] Estimating duration from bitrate, this may be inaccurate
  
  Input #1, srt, from 'hifi.srt':
  
    Duration: N/A, start: 56.080000, bitrate: N/A
  
      Stream #1.0: Subtitle: srt
  
  File 'hifi.m4v' already exists. Overwrite ? [y/N] y
  
  [buffer @ 02548920] w:544 h:304 pixfmt:yuv420p tb:1/1000000 sar:1/1 sws_param:
  
  [scale @ 02558ee0] w:544 h:304 fmt:yuv420p -> w:480 h:240 fmt:yuv420p flags:0x4
  
  [libx264 @ 02547f20] Default settings detected, using medium profile
  
  [libx264 @ 02547f20] using SAR=1/1
  
  [libx264 @ 02547f20] using cpu capabilities: MMX2 SSE2Fast SSSE3 FastShuffle SSE4.1 Cache64
  
  [libx264 @ 02547f20] profile High, level 3.0
  
  [libx264 @ 02547f20] 264 - core 115 - H.264/MPEG-4 AVC codec - Copyleft 2003-2011 - 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=-2 threads=1 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=0 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=256 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=10000 vbv_bufsize=10000 nal_hrd=none ip_ratio=1.40 aq=1:1.00
  
  Output #0, ipod, to 'hifi.m4v':
  
      Stream #0.0: Video: libx264, yuv420p, 480x240 [SAR 1:1 DAR 2:1], q=2-31, 256 kb/s, 90k tbn, 25 tbc
  
      Stream #0.1: Audio: libfaac, 48000 Hz, 2 channels, s16, 128 kb/s
  
      Stream #0.2: Subtitle: srt
  
      Stream #0.3: Subtitle: [0][0][0][0] / 0x0000, 64 kb/s
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
    Stream #0.1 -> #0.1
  
    Stream #1.0 -> #0.2
  
    Stream #1.0 -> #0.3
  
  Encoder (codec id 0) not found for output stream #0.3

  can anyone tell what wrong with my command ??

  thanks,