FFMPEG 与 -var_stream_map 的流索引匹配不正确

Question

我正在使用 bash 脚本运行 FFMPEG 命令来打开一个名为 Awoo.mkv 的输入文件。分成三个 HLS 播放列表，每个播放列表具有不同的分辨率、视频和音频比特率。

这是脚本:

name=gw

rm /tmp/hls/*

./ffmpeg -y \
    -stream_loop -1 -re \
    -i Awoo.mkv \
    -b:v:0 4000k -b:a:0 512k -s:0 1920x1080 -r:0 30 -g:0 90 -preset:0 superfast -tune:0 zerolatency -profile:v:0 high -level:v:0 4 \
    -b:v:1 2500k -b:a:1 256k -s:1 1280x720 -r:1 30 -g:1 90 -preset:1 superfast -tune:1 zerolatency -profile:v:1 high -level:v:1 4 \
    -b:v:2 800k -b:a:2 255k -s:2 960x540 -r:2 30 -g:2 90 -preset:2 superfast -tune:2 zerolatency -profile:v:2 high -level:v:2 4 \
    -hls_time 6 \
    -hls_list_size 2 \
    -hls_flags delete_segments \
    -map 0:v -map 0:a -map 0:v -map 0:a -map 0:v -map 0:a \
    -var_stream_map "v:0,a:0 v:1,a:1 v:2,a:2" \
    -f hls -master_pl_name "${name}.m3u8" \
    -hls_segment_filename "/tmp/hls/${name}_-%d-%v.ts" \
    "/tmp/hls/${name}_%v.m3u8"

这几乎可以很好地工作，但输出略有偏差......

如果你看这两行:

-b:v:1 2500k -b:a:1 256k -s:1 1280x720 -r:1 30 -g:1 90 -preset:1 superfast -tune:1 zerolatency -profile:v:1 high -level:v:1 4 \
-b:v:2 800k -b:a:2 255k -s:2 960x540 -r:2 30 -g:2 90 -preset:2 superfast -tune:2 zerolatency -profile:v:2 high -level:v:2 4 \

1280x720 的分辨率应该有 2500k 的比特率，960x540 的分辨率应该有 800k 的比特率。

这是 FFMPEG 的相关输出:

Stream #0:2(und): Video: h264 (libx264), yuv420p(progressive), 960x540 [SAR 1:1 DAR 16:9], q=-1--1, 2500 kb/s, 30 fps, 90k tbn, 30 tbc (default)
Metadata:
  CREATION_TIME   : 2017-01-27 05:02:53
  LANGUAGE        : und
  HANDLER_NAME    : VideoHandler
  DURATION        : 00:02:24.310000000
  encoder         : Lavc58.18.100 libx264
Side data:
  cpb: bitrate max/min/avg: 0/0/2500000 buffer size: 0 vbv_delay: -1
Stream #0:3(eng): Audio: aac (LC), 44100 Hz, stereo, fltp, 256 kb/s (default)
Metadata:
  LANGUAGE        : eng
  DURATION        : 00:02:24.348000000
  encoder         : Lavc58.18.100 aac
Stream #0:4(und): Video: h264 (libx264), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 800 kb/s, 29 fps, 90k tbn, 29 tbc (default)
Metadata:
  CREATION_TIME   : 2017-01-27 05:02:53
  LANGUAGE        : und
  HANDLER_NAME    : VideoHandler
  DURATION        : 00:02:24.310000000
  encoder         : Lavc58.18.100 libx264
Side data:
  cpb: bitrate max/min/avg: 0/0/800000 buffer size: 0 vbv_delay: -1
Stream #0:5(eng): Audio: aac (LC), 44100 Hz, stereo, fltp, 255 kb/s (default)
Metadata:
  LANGUAGE        : eng
  DURATION        : 00:02:24.348000000
  encoder         : Lavc58.18.100 aac

流 #0:2 的分辨率错误为 960x540，因此比特率也错误为 2500。这应该是 1280x720 的分辨率，但下面与 800 的比特率匹配。

据我所知，分辨率显示的顺序是错误的，如果首先是 720，然后是 540，那么一切都会匹配得很好。我不确定是什么原因造成的，我是 -var_stream_map 的新手.

如果相关，FFMPEG 的整个输出如下:

ffmpeg version 4.0.3-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg
  libavutil      56. 14.100 / 56. 14.100
  libavcodec     58. 18.100 / 58. 18.100
  libavformat    58. 12.100 / 58. 12.100
  libavdevice    58.  3.100 / 58.  3.100
  libavfilter     7. 16.100 /  7. 16.100
  libswscale      5.  1.100 /  5.  1.100
  libswresample   3.  1.100 /  3.  1.100
  libpostproc    55.  1.100 / 55.  1.100
Input #0, matroska,webm, from 'Awoo.mkv':
  Metadata:
    COMPATIBLE_BRANDS: iso6avc1mp41
    MAJOR_BRAND     : dash
    MINOR_VERSION   : 0
    ENCODER         : Lavf56.40.101
  Duration: 00:02:24.35, start: 0.000000, bitrate: 1114 kb/s
    Stream #0:0(und): Video: h264 (Main), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], 29 fps, 29 tbr, 1k tbn, 58 tbc (default)
    Metadata:
      CREATION_TIME   : 2017-01-27 05:02:53
      LANGUAGE        : und
      HANDLER_NAME    : VideoHandler
      DURATION        : 00:02:24.310000000
    Stream #0:1(eng): Audio: vorbis, 44100 Hz, stereo, fltp (default)
    Metadata:
      LANGUAGE        : eng
      DURATION        : 00:02:24.348000000
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:1 (vorbis (native) -> aac (native))
  Stream #0:0 -> #0:2 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:3 (vorbis (native) -> aac (native))
  Stream #0:0 -> #0:4 (h264 (native) -> h264 (libx264))
  Stream #0:1 -> #0:5 (vorbis (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x664d1c0] using SAR=1/1
[libx264 @ 0x664d1c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x664d1c0] profile High, level 4.0, 4:2:0, 8-bit
[libx264 @ 0x664d1c0] 264 - core 157 r2935 545de2f - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - options: cabac=1 ref=1 deblock=1:0:0 analyse=0x3:0x3 me=dia subme=1 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=4 lookahead_threads=4 sliced_threads=1 slices=4 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=1 keyint=90 keyint_min=9 scenecut=40 intra_refresh=0 rc=abr mbtree=0 bitrate=4000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[libx264 @ 0x664f080] using SAR=1/1
[libx264 @ 0x664f080] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x664f080] profile High, level 4.0, 4:2:0, 8-bit
[libx264 @ 0x664f080] 264 - core 157 r2935 545de2f - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - options: cabac=1 ref=1 deblock=1:0:0 analyse=0x3:0x3 me=dia subme=1 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=0 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=4 lookahead_threads=4 sliced_threads=1 slices=4 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=1 keyint=90 keyint_min=9 scenecut=40 intra_refresh=0 rc=abr mbtree=0 bitrate=2500 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[libx264 @ 0x6680b80] using SAR=1/1
[libx264 @ 0x6680b80] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x6680b80] profile High, level 4.0, 4:2:0, 8-bit
[libx264 @ 0x6680b80] 264 - core 157 r2935 545de2f - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - 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=6 lookahead_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=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=800 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[hls @ 0x6650000] Opening '/tmp/hls/gw_-0-0.ts' for writing
[hls @ 0x6650000] Opening '/tmp/hls/gw_-0-1.ts' for writing
[hls @ 0x6650000] Opening '/tmp/hls/gw_-0-2.ts' for writing
Output #0, hls, to '/tmp/hls/gw_%v.m3u8':
  Metadata:
    COMPATIBLE_BRANDS: iso6avc1mp41
    MAJOR_BRAND     : dash
    MINOR_VERSION   : 0
    encoder         : Lavf58.12.100
    Stream #0:0(und): Video: h264 (libx264), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=-1--1, 4000 kb/s, 30 fps, 90k tbn, 30 tbc (default)
    Metadata:
      CREATION_TIME   : 2017-01-27 05:02:53
      LANGUAGE        : und
      HANDLER_NAME    : VideoHandler
      DURATION        : 00:02:24.310000000
      encoder         : Lavc58.18.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/4000000 buffer size: 0 vbv_delay: -1
    Stream #0:1(eng): Audio: aac (LC), 44100 Hz, stereo, fltp, 512 kb/s (default)
    Metadata:
      LANGUAGE        : eng
      DURATION        : 00:02:24.348000000
      encoder         : Lavc58.18.100 aac
    Stream #0:2(und): Video: h264 (libx264), yuv420p(progressive), 960x540 [SAR 1:1 DAR 16:9], q=-1--1, 2500 kb/s, 30 fps, 90k tbn, 30 tbc (default)
    Metadata:
      CREATION_TIME   : 2017-01-27 05:02:53
      LANGUAGE        : und
      HANDLER_NAME    : VideoHandler
      DURATION        : 00:02:24.310000000
      encoder         : Lavc58.18.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/2500000 buffer size: 0 vbv_delay: -1
    Stream #0:3(eng): Audio: aac (LC), 44100 Hz, stereo, fltp, 256 kb/s (default)
    Metadata:
      LANGUAGE        : eng
      DURATION        : 00:02:24.348000000
      encoder         : Lavc58.18.100 aac
    Stream #0:4(und): Video: h264 (libx264), yuv420p, 1280x720 [SAR 1:1 DAR 16:9], q=-1--1, 800 kb/s, 29 fps, 90k tbn, 29 tbc (default)
    Metadata:
      CREATION_TIME   : 2017-01-27 05:02:53
      LANGUAGE        : und
      HANDLER_NAME    : VideoHandler
      DURATION        : 00:02:24.310000000
      encoder         : Lavc58.18.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/800000 buffer size: 0 vbv_delay: -1
    Stream #0:5(eng): Audio: aac (LC), 44100 Hz, stereo, fltp, 255 kb/s (default)
    Metadata:
      LANGUAGE        : eng
      DURATION        : 00:02:24.348000000
      encoder         : Lavc58.18.100 aac
[hls @ 0x6650000] Opening '/tmp/hls/gw_0.m3u8.tmp' for writing6.50 bitrate=N/A dup=12 drop=0 speed=0.965x    
[hls @ 0x6650000] Opening '/tmp/hls/gw_1.m3u8.tmp' for writing
[hls @ 0x6650000] Opening '/tmp/hls/gw_2.m3u8.tmp' for writing
[hls @ 0x6650000] Opening '/tmp/hls/gw.m3u8' for writing

Answer 1

没有流类型前缀的流说明符将被视为绝对流索引。所以，-b:v:1 2500k适用于第二个视频输出流，但 -s:1 1280x720适用于第二个输出流，根据您的映射，它是一个音频流。尽管选项可以是特定于媒体的，但流说明符是以不可知的方式评估的。