我正在使用三个音频/视频文件创建“画中画”音频/视频文件。
转换已完成，但播放完成的视频文件时没有音频。我经常进行此类转换，没有遇到任何问题。但是，这个特定的视频出现了问题。我不确定为什么在完成的视频中听不到音频流。
ffmpeg -i 9318_segment_1_remote_0.mp4 -i 9318_segment_1_remote_1.mp4 -i 9318_segment_1_local_0.mp4 \
-filter_complex \
" [1:v]scale=203.33333333333:-1:flags=lanczos,setpts='if(eq(N,0),PTS,PTS+0.228/TB)',fps=30[rem1setpts]; \
[2:v]scale=203.33333333333:-1:flags=lanczos[loc0]; \
[0:v]setpts='if(eq(N,0),PTS,PTS+0.311/TB)',fps=30[1setpts]; \
[1setpts][loc0]overlay=main_w-overlay_w-10:main_h-overlay_h-10[rem0]; \
[rem0][rem1setpts]overlay=main_w-overlay_w-180:main_h-overlay_h-10[rem1]; \
[0:a]adelay=311|311[0a]; \
[1:a]adelay=228|228[1a]; \
[0a][1a][2:a]amerge=inputs=3[a]" \
-map "[rem1]" -map "[a]" -ac 3 \
-vcodec libx264 \
-ar 44100 -acodec aac \
9318_segment_1.mp4
命令结果：
ffmpeg version n4.0.2-65-g938bc91 Copyright (c) 2000-2018 the FFmpeg developers
built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
configuration: --prefix=/home/daryl/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/daryl/ffmpeg_build/include --extra-ldflags=-L/home/daryl/ffmpeg_build/lib --extra-libs=-lpthread --bindir=/home/daryl/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree
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, mov,mp4,m4a,3gp,3g2,mj2, from '9318_segment_1_remote_0.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.12.100
Duration: 00:00:24.61, start: 0.000000, bitrate: 326 kb/s
Stream #0:0(und): Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, mono, fltp, 96 kb/s (default)
Metadata:
handler_name : SoundHandler
Side data:
audio service type: main
Stream #0:1(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 227 kb/s, 16.67 fps, 16.67 tbr, 12800 tbn, 33.33 tbc (default)
Metadata:
handler_name : VideoHandler
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from '9318_segment_1_remote_1.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.12.100
Duration: 00:00:24.54, start: 0.000000, bitrate: 400 kb/s
Stream #1:0(und): Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, mono, fltp, 96 kb/s (default)
Metadata:
handler_name : SoundHandler
Side data:
audio service type: main
Stream #1:1(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 301 kb/s, 16.67 fps, 16.67 tbr, 12800 tbn, 33.33 tbc (default)
Metadata:
handler_name : VideoHandler
Input #2, mov,mp4,m4a,3gp,3g2,mj2, from '9318_segment_1_local_0.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.12.100
Duration: 00:00:24.86, start: 0.000000, bitrate: 468 kb/s
Stream #2:0(und): Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, mono, fltp, 96 kb/s (default)
Metadata:
handler_name : SoundHandler
Side data:
audio service type: main
Stream #2:1(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 369 kb/s, 16.67 fps, 16.67 tbr, 12800 tbn, 33.33 tbc (default)
Metadata:
handler_name : VideoHandler
Stream mapping:
Stream #0:0 (ac3) -> adelay
Stream #0:1 (h264) -> setpts
Stream #1:0 (ac3) -> adelay
Stream #1:1 (h264) -> scale
Stream #2:0 (ac3) -> amerge:in2
Stream #2:1 (h264) -> scale
overlay -> Stream #0:0 (libx264)
amerge -> Stream #0:1 (aac)
Press [q] to stop, [?] for help
[Parsed_amerge_10 @ 0x35b8d80] No channel layout for input 1
[Parsed_amerge_10 @ 0x35b8d80] Input channel layouts overlap: output layout will be determined by the number of distinct input channels
[libx264 @ 0x2cfd200] using SAR=1/1
[libx264 @ 0x2cfd200] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
[libx264 @ 0x2cfd200] profile High, level 3.0
[libx264 @ 0x2cfd200] 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=-2 threads=1 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=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
[aac @ 0x2d03740] Using a PCE to encode channel layout
Output #0, mp4, to '9318_segment_1.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.12.100
Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p, 640x480 [SAR 1:1 DAR 4:3], q=-1--1, 30 fps, 15360 tbn, 30 tbc (default)
Metadata:
encoder : Lavc58.18.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, 2.1, fltp, 144 kb/s (default)
Metadata:
encoder : Lavc58.18.100 aac
frame= 746 fps= 49 q=29.0 Lsize= 982kB time=00:00:24.76 bitrate= 324.9kbits/s speed=1.62x
video:800kB audio:154kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.881939%
[libx264 @ 0x2cfd200] frame I:3 Avg QP:17.42 size: 23901
[libx264 @ 0x2cfd200] frame P:221 Avg QP:19.93 size: 2688
[libx264 @ 0x2cfd200] frame B:522 Avg QP:23.95 size: 293
[libx264 @ 0x2cfd200] consecutive B-frames: 6.3% 1.1% 0.4% 92.2%
[libx264 @ 0x2cfd200] mb I I16..4: 29.7% 39.5% 30.8%
[libx264 @ 0x2cfd200] mb P I16..4: 2.5% 3.0% 0.4% P16..4: 31.9% 6.2% 4.2% 0.0% 0.0% skip:51.8%
[libx264 @ 0x2cfd200] mb B I16..4: 0.0% 0.1% 0.0% B16..8: 19.4% 0.4% 0.1% direct: 0.3% skip:79.7% L0:46.9% L1:52.2% BI: 0.9%
[libx264 @ 0x2cfd200] 8x8 transform intra:49.6% inter:79.6%
[libx264 @ 0x2cfd200] coded y,uvDC,uvAC intra: 31.4% 47.9% 15.2% inter: 3.0% 7.2% 0.2%
[libx264 @ 0x2cfd200] i16 v,h,dc,p: 26% 16% 16% 42%
[libx264 @ 0x2cfd200] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 19% 16% 45% 3% 3% 3% 4% 4% 4%
[libx264 @ 0x2cfd200] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 22% 27% 13% 5% 7% 7% 7% 6% 6%
[libx264 @ 0x2cfd200] i8c dc,h,v,p: 57% 24% 17% 3%
[libx264 @ 0x2cfd200] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x2cfd200] ref P L0: 67.9% 5.7% 17.3% 9.0%
[libx264 @ 0x2cfd200] ref B L0: 89.5% 8.0% 2.6%
[libx264 @ 0x2cfd200] ref B L1: 97.0% 3.0%
[libx264 @ 0x2cfd200] kb/s:263.43
[aac @ 0x2d03740] Qavg: 59644.461
完成的文件包含以下详细信息。
ffmpeg -i 9318_segment_1.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '9318_segment_1.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf58.12.100
Duration: 00:00:24.87, start: 0.000000, bitrate: 323 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x480 [SAR 1:1 DAR 4:3], 263 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
Metadata:
handler_name : VideoHandler
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, 2.1, fltp, 51 kb/s (default)
Metadata:
handler_name : SoundHandler
据我所知，“amerge 以最短的输入终止”。因此，我尝试了一些不同的选项，将 apad 添加到输入 0 和 1。但是，这三个文件的持续时间相似，所以我应该听到一些音频。
- 9318_segment_1_remote_0.mp4 - 时长：00:00:24.61（开始于 0.311 秒）
- 9318_segment_1_remote_1.mp4 - 时长：00:00:24.54（从 0.228 秒开始）
- 9318_segment_1_local_0.mp4 - 时长：00:00:24.86（从 0.0000 秒开始）
知道为什么在这种情况下输出文件中没有可听见的音频吗？
答案1
您遇到了 amerge 过滤器的一个限制。它根据输出通道数分配通道布局。对于 3 个通道，第一个可用布局是2.1。Front Left + Front Right + Low Frequency Effects因此，第三个输入（来自9318_segment_1_local_0.mp4）在编码时，其大部分频率将被剥离，其目的地将被标记为低音炮 :)。对于 3 个通道，有更好的布局，但在这种情况下，amerge 将选择第一个。
一种部分补救措施是切换输入的顺序，以便承载内容的流位于第一或第二。
更好的补救措施是使用 amix 过滤器，它会将所有输入合并到单个可听见的通道 --> [0a][1a][2:a]amix=inputs=3[a]。删除-ac 3。