为什么使用 ffmpeg 从 png 文件创建的 mp4 文件的持续时间比预期的要短？
Why duration of the mp4 file created with ffmpeg from png files is smaller than expected?
我正在尝试使用 ffmpeg 将一堆 png 文件连接成一个 mp4 文件。我使用以下命令：
ffmpeg -f concat -i concat.txt -f mp4 out.mp4
“描述文件”（concat.txt）如下所示：
file screen_001.png
duration 0.14538311958312988
file screen_002.png
duration 0.11382007598876953
file screen_003.png
duration 2.543360710144043
...
file screen_036.png
duration 0.15303301811218262
file screen_037.png
duration 0.160630464553833
file screen_038.png
duration 3.2751874923706055
鉴于命令有效，我能够创建所需的 mp4 文件。问题是，输出文件的持续时间小于 concat.txt 中 duration 行的总和。我希望 mp4 文件长 ~22.48s 但我得到 19.20s 长文件。
我做错了什么？也许我没有使用我应该使用的标志？甚至可以做我想做的事吗？我是一个新手 ffmpeg 和视频操作，所以任何帮助将不胜感激。
ffmpeg 的输出，也许会有用：
root@65181939e08e:/files/tmp# ffmpeg -f concat -i concat.txt -f mp4 out.mp4
ffmpeg version 4.1.6-1~deb10u1 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Input #0, concat, from 'concat.txt':
Duration: 00:00:22.48, start: 0.000000, bitrate: 0 kb/s
Stream #0:0: Video: png, rgba(pc), 1366x768, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
Stream #0:0 -> #0:0 (png (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x5651f1a6e8c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x5651f1a6e8c0] profile High 4:4:4 Predictive, level 3.2, 4:4:4 8-bit
[libx264 @ 0x5651f1a6e8c0] 264 - core 155 r2917 0a84d98 - 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=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 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
Output #0, mp4, to 'out.mp4':
Metadata:
encoder : Lavf58.20.100
Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv444p, 1366x768, q=-1--1, 25 fps, 12800 tbn, 25 tbc
Metadata:
encoder : Lavc58.35.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame= 483 fps=199 q=-1.0 Lsize= 258kB time=00:00:19.20 bitrate= 110.2kbits/s dup=445 drop=0 speed=7.89x
video:252kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.564829%
[libx264 @ 0x5651f1a6e8c0] frame I:5 Avg QP: 7.86 size: 28761
[libx264 @ 0x5651f1a6e8c0] frame P:121 Avg QP:14.58 size: 729
[libx264 @ 0x5651f1a6e8c0] frame B:357 Avg QP:13.34 size: 70
[libx264 @ 0x5651f1a6e8c0] consecutive B-frames: 1.2% 0.0% 1.9% 96.9%
[libx264 @ 0x5651f1a6e8c0] mb I I16..4: 88.2% 0.0% 11.8%
[libx264 @ 0x5651f1a6e8c0] mb P I16..4: 1.3% 0.0% 0.3% P16..4: 0.2% 0.0% 0.0% 0.0% 0.0% skip:98.1%
[libx264 @ 0x5651f1a6e8c0] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 0.9% 0.0% 0.0% direct: 0.0% skip:99.1% L0:59.4% L1:40.6% BI: 0.0%
[libx264 @ 0x5651f1a6e8c0] coded y,u,v intra: 7.9% 0.7% 1.3% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x5651f1a6e8c0] i16 v,h,dc,p: 81% 18% 1% 0%
[libx264 @ 0x5651f1a6e8c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 33% 28% 22% 2% 3% 3% 3% 3% 3%
[libx264 @ 0x5651f1a6e8c0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x5651f1a6e8c0] ref P L0: 72.5% 11.9% 12.4% 3.1%
[libx264 @ 0x5651f1a6e8c0] ref B L0: 50.4% 48.1% 1.4%
[libx264 @ 0x5651f1a6e8c0] ref B L1: 98.9% 1.1%
[libx264 @ 0x5651f1a6e8c0] kb/s:106.45
感谢您的帮助！
像这样从每个 png 创建一个视频：
ffmpeg -f image2 -loop 1 -i 01.png -r 30 -t 00:00:05.000 -pix_fmt yuv420p 01.mp4
在哪里：
"-r 30" 是帧率
"-t 00:00:05.000" 是这个 PNG 在视频中的时间，在这种情况下是 5 秒，看这个浮点数是 3 ： (
无论如何，为每个视频制作这个并连接它，创建一个 txt：
concat.txt
file '01.mp4'
file '02.mp4'
并使用 ffmpeg 连接所有文件
ffmpeg -f concat -safe 0 -i concat.txt -c copy output.mp4
祝你好运！
文档中的编辑也以微秒为单位，可能浮点数是 6 而不是 3:
http://www.ffmpeg.org/ffmpeg-utils.html#time-duration-syntax
我正在尝试使用 ffmpeg 将一堆 png 文件连接成一个 mp4 文件。我使用以下命令：
ffmpeg -f concat -i concat.txt -f mp4 out.mp4
“描述文件”（concat.txt）如下所示：
file screen_001.png
duration 0.14538311958312988
file screen_002.png
duration 0.11382007598876953
file screen_003.png
duration 2.543360710144043
...
file screen_036.png
duration 0.15303301811218262
file screen_037.png
duration 0.160630464553833
file screen_038.png
duration 3.2751874923706055
鉴于命令有效，我能够创建所需的 mp4 文件。问题是，输出文件的持续时间小于 concat.txt 中 duration 行的总和。我希望 mp4 文件长 ~22.48s 但我得到 19.20s 长文件。
我做错了什么？也许我没有使用我应该使用的标志？甚至可以做我想做的事吗？我是一个新手 ffmpeg 和视频操作，所以任何帮助将不胜感激。
ffmpeg 的输出，也许会有用：
root@65181939e08e:/files/tmp# ffmpeg -f concat -i concat.txt -f mp4 out.mp4
ffmpeg version 4.1.6-1~deb10u1 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
libavutil 56. 22.100 / 56. 22.100
libavcodec 58. 35.100 / 58. 35.100
libavformat 58. 20.100 / 58. 20.100
libavdevice 58. 5.100 / 58. 5.100
libavfilter 7. 40.101 / 7. 40.101
libavresample 4. 0. 0 / 4. 0. 0
libswscale 5. 3.100 / 5. 3.100
libswresample 3. 3.100 / 3. 3.100
libpostproc 55. 3.100 / 55. 3.100
Input #0, concat, from 'concat.txt':
Duration: 00:00:22.48, start: 0.000000, bitrate: 0 kb/s
Stream #0:0: Video: png, rgba(pc), 1366x768, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
Stream #0:0 -> #0:0 (png (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x5651f1a6e8c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x5651f1a6e8c0] profile High 4:4:4 Predictive, level 3.2, 4:4:4 8-bit
[libx264 @ 0x5651f1a6e8c0] 264 - core 155 r2917 0a84d98 - 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=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 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
Output #0, mp4, to 'out.mp4':
Metadata:
encoder : Lavf58.20.100
Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv444p, 1366x768, q=-1--1, 25 fps, 12800 tbn, 25 tbc
Metadata:
encoder : Lavc58.35.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
frame= 483 fps=199 q=-1.0 Lsize= 258kB time=00:00:19.20 bitrate= 110.2kbits/s dup=445 drop=0 speed=7.89x
video:252kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.564829%
[libx264 @ 0x5651f1a6e8c0] frame I:5 Avg QP: 7.86 size: 28761
[libx264 @ 0x5651f1a6e8c0] frame P:121 Avg QP:14.58 size: 729
[libx264 @ 0x5651f1a6e8c0] frame B:357 Avg QP:13.34 size: 70
[libx264 @ 0x5651f1a6e8c0] consecutive B-frames: 1.2% 0.0% 1.9% 96.9%
[libx264 @ 0x5651f1a6e8c0] mb I I16..4: 88.2% 0.0% 11.8%
[libx264 @ 0x5651f1a6e8c0] mb P I16..4: 1.3% 0.0% 0.3% P16..4: 0.2% 0.0% 0.0% 0.0% 0.0% skip:98.1%
[libx264 @ 0x5651f1a6e8c0] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 0.9% 0.0% 0.0% direct: 0.0% skip:99.1% L0:59.4% L1:40.6% BI: 0.0%
[libx264 @ 0x5651f1a6e8c0] coded y,u,v intra: 7.9% 0.7% 1.3% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x5651f1a6e8c0] i16 v,h,dc,p: 81% 18% 1% 0%
[libx264 @ 0x5651f1a6e8c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 33% 28% 22% 2% 3% 3% 3% 3% 3%
[libx264 @ 0x5651f1a6e8c0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x5651f1a6e8c0] ref P L0: 72.5% 11.9% 12.4% 3.1%
[libx264 @ 0x5651f1a6e8c0] ref B L0: 50.4% 48.1% 1.4%
[libx264 @ 0x5651f1a6e8c0] ref B L1: 98.9% 1.1%
[libx264 @ 0x5651f1a6e8c0] kb/s:106.45
感谢您的帮助！
像这样从每个 png 创建一个视频：
ffmpeg -f image2 -loop 1 -i 01.png -r 30 -t 00:00:05.000 -pix_fmt yuv420p 01.mp4
在哪里： "-r 30" 是帧率
"-t 00:00:05.000" 是这个 PNG 在视频中的时间，在这种情况下是 5 秒，看这个浮点数是 3 ： (
无论如何，为每个视频制作这个并连接它，创建一个 txt：
concat.txt
file '01.mp4'
file '02.mp4'
并使用 ffmpeg 连接所有文件
ffmpeg -f concat -safe 0 -i concat.txt -c copy output.mp4
祝你好运！
文档中的编辑也以微秒为单位，可能浮点数是 6 而不是 3:
http://www.ffmpeg.org/ffmpeg-utils.html#time-duration-syntax