FFmpeg转码（2）

FFmpeg音频转码

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FFmpeg输出MP3

1. 查看参数，使用之前需要先下载安装libmp3lame

ffmpeg -h encoder=libmp3lame

Encoder libmp3lame [libmp3lame MP3 (MPEG audio layer 3)]:
    General capabilities: delay small 
    Threading capabilities: none
    Supported sample rates: 44100 48000 32000 22050 24000 16000 11025 12000 8000
    Supported sample formats: s32p fltp s16p
    Supported channel layouts: mono stereo
libmp3lame encoder AVOptions:
  -reservoir             E...A.... use bit reservoir (default true)
  -joint_stereo          E...A.... use joint stereo (default true)
  -abr                   E...A.... use ABR (default false)

2. MP3的转换

ffmpeg -i input.mp4 -acodec libmp3lame OUTPUT.mp3

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.19.100
  Duration: 00:00:30.32, start: 0.000000, bitrate: 397 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x208 [SAR 16:15 DAR 32:13], 261 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Stream mapping:
  Stream #0:1 -> #0:0 (aac (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to 'OUTPUT.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    TSSE            : Lavf58.20.100
    Stream #0:0(und): Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp (default)
    Metadata:
      handler_name    : SoundHandler
      encoder         : Lavc58.35.100 libmp3lame
size=     474kB time=00:00:30.30 bitrate= 128.2kbits/s speed=43.5x    
video:0kB audio:474kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.073364%

3. 设置VBR参数

ffmpeg -i input.mp3 -acodec libmp3lame -q:a 8 output.mp3

Input #0, mp3, from 'input.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:00:30.33, start: 0.025057, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc58.35
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (mp3float) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to 'output.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    TSSE            : Lavf58.20.100
    Stream #0:0: Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp
    Metadata:
      encoder         : Lavc58.35.100 libmp3lame
size=     280kB time=00:00:30.30 bitrate=  75.6kbits/s speed=52.7x    
video:0kB audio:279kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.124486%

4. 设置CBR参数

ffmpeg -i input.mp3 -acodec libmp3lame -b:a 64k output.mp3

Input #0, mp3, from 'input.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:00:30.33, start: 0.025057, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc58.35
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (mp3float) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to 'output.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    TSSE            : Lavf58.20.100
    Stream #0:0: Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp, 64 kb/s
    Metadata:
      encoder         : Lavc58.35.100 libmp3lame
size=     237kB time=00:00:30.30 bitrate=  64.1kbits/s speed=40.3x    
video:0kB audio:237kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.146728%

5.设置ABR参数

ffmpeg -i input.mp3 -acodec libmp3lame -b:a 64k -abr 1 output.mp3

Input #0, mp3, from 'input.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:00:30.33, start: 0.025057, bitrate: 128 kb/s
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc58.35
Stream mapping:
  Stream #0:0 -> #0:0 (mp3 (mp3float) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
Output #0, mp3, to 'output.mp3':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    TSSE            : Lavf58.20.100
    Stream #0:0: Audio: mp3 (libmp3lame), 44100 Hz, stereo, fltp, 64 kb/s
    Metadata:
      encoder         : Lavc58.35.100 libmp3lame
size=     264kB time=00:00:30.30 bitrate=  71.4kbits/s speed=40.9x    
video:0kB audio:264kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.131777%

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FFmpeg输出AAC

动态码率(VBR)的AAC的级别中有三种编码信息，分为：

• LC：Low Complexity AAC，这种编码相对来说体积比较小，质量稍差
• HE：High-Efficiency AAC，这种编码相对来说体积稍小，质量较好
• HEv2：High-Efficiency AAC version 2，这种编码相对来说体积小，质量优

FFmpeg支持AAC的三种编码器：

• aac：FFmpeg本身的AAC编码实现
• libfaac：第三方的AAC编码器
• libfdk_aac：第三方的AAC编码器

以上三种质量顺序为：libfdk_aac > aac > libfaac

1. 转码为AAC音频，码率为160kbit/s

ffmpeg -i input.mp4 -c:a aac -b:a 160k output.aac

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.19.100
  Duration: 00:00:30.32, start: 0.000000, bitrate: 397 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 480x208 [SAR 16:15 DAR 32:13], 261 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
Stream mapping:
  Stream #0:1 -> #0:0 (aac (native) -> aac (native))
Press [q] to stop, [?] for help
Output #0, adts, to 'output.aac':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
    Stream #0:0(und): Audio: aac (LC), 44100 Hz, stereo, fltp, 160 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      encoder         : Lavc58.35.100 aac
size=     606kB time=00:00:30.30 bitrate= 163.7kbits/s speed=  66x    
video:0kB audio:597kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.496385%
[aac @ 0x7fdc93027800] Qavg: 506.964

2. 设置VBR参数（qscale：0.1～2）

ffmpeg -i input.wav -c:a aac -q:a 2 output.m4a

Input #0, wav, from 'input.wav':
  Duration: 00:03:43.00, bitrate: 1411 kb/s
    Stream #0:0: Audio: dts (DTS-ES) ([1][0][0][0] / 0x0001), 44100 Hz, 6.1, fltp, 1411 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (dts (dca) -> aac (native))
Press [q] to stop, [?] for help
[aac @ 0x7fb289002e00] Using a PCE to encode channel layout "6.1"
Output #0, ipod, to 'output.m4a':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, 6.1, fltp, 463 kb/s
    Metadata:
      encoder         : Lavc58.35.100 aac
size=   18773kB time=00:03:43.00 bitrate= 689.6kbits/s speed=21.4x    
video:0kB audio:18735kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.205963%
[aac @ 0x7fb289002e00] Qavg: 236.000