我想在使用 ffplay 播放视频时显示视频的当前帧号。我已经看过this解决方案，但是当我寻找视频的任何部分时，计数器会重置。有一个变量，start_number , ffplay 文档说是 The starting frame number for the n/frame_num variable. The default value is "0".似乎 n 设置为在开始视频或在 I 帧之间搜索时设置的值。我想将此变量设置为 %{floor(t*60)}将解决我的问题，但运行此之后:
ffplay -i "video.mp4" -vf drawtext="fontsize=30:box=1:boxcolor=white:fontcolor=black:fontfile=/Windows/Fonts/arial.ttf:start_number=floor(t*60):text=%{n}"
我得到以下控制台输出:
ffplay version N-84679-gd65b595 Copyright (c) 2003-2017 the FFmpeg developers
built with gcc 6.3.0 (GCC)
configuration: --enable-gpl --enable-version3 --enable-cuda --enable-cuvid --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-zlib
libavutil 55. 51.100 / 55. 51.100
libavcodec 57. 86.103 / 57. 86.103
libavformat 57. 67.100 / 57. 67.100
libavdevice 57. 3.101 / 57. 3.101
libavfilter 6. 78.100 / 6. 78.100
libswscale 4. 3.101 / 4. 3.101
libswresample 2. 4.100 / 2. 4.100
libpostproc 54. 2.100 / 54. 2.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video.mp4':= 0B f=0/0
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
creation_time : 2017-03-30T02:49:20.000000Z
encoder : Open Broadcaster Software v0.659b
Duration: 00:05:36.85, start: 0.000000, bitrate: 72636 kb/s
Stream #0:0(eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 162 kb/s (default)
Metadata:
creation_time : 2017-03-30T02:49:20.000000Z
handler_name : Sound Media Handler
Stream #0:1(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuv420p(tv, bt709/bt709/iec61966-2-1), 2560x1440, 72465 kb/s, 60 fps, 60 tbr, 1k tbn, 120 tbc (default)
Metadata:
creation_time : 2017-03-30T02:49:20.000000Z
handler_name : Video Media Handler
encoder : AVC Coding
[drawtext @ 00000000122770e0] [Eval @ 0000000008f3eb60] Undefined constant or missing '(' in 't*60)'
[drawtext @ 00000000122770e0] Unable to parse option value "floor(t*60)"
[drawtext @ 00000000122770e0] [Eval @ 0000000008f3ebd0] Undefined constant or missing '(' in 't*60)'
[drawtext @ 00000000122770e0] Unable to parse option value "floor(t*60)"
[drawtext @ 00000000122770e0] Error setting option start_number to value floor(t*60).
[Parsed_drawtext_0 @ 000000000263eca0] Error applying options to the filter.
Error initializing filter 'drawtext' with args 'fontsize=30:box=1:boxcolor=white:fontcolor=black:fontfile=/Windows/Fonts/arial.ttf:start_number=floor(t*60):text=%{n}'
0.01 A-V: nan fd= 0 aq= 22KB vq= 5866KB sq= 0B f=0/0
事实上，
start_number 中的任何变量的赋值调用此错误。我不知道我是否有正确的语法，但这是否意味着它不评估表达式？或者它可能出于某种原因不接受变量？在那之后，我尝试将文本设置为
%{t} ，播放视频，但反复报此错误，左上角没有文字:[Parsed_drawtext_0 @ 0000000003e54ea0] %{t} is not known 0B f=0/0
那么当前时间变量在drawtext中不起作用吗？
是否有另一种方法可以在视频甚至控制台窗口上写入当前帧？
目前使用 Windows 10 Enterprise 和最新版本的 ffplay for windows。
最佳答案
假设视频是恒定帧速率 60 fps，请使用
ffplay -i "video.mp4"
-vf "drawtext="fontsize=30:box=1:boxcolor=white:fontcolor=black:fontfile=/Windows/Fonts/arial.ttf:text='%{eif\:t*60\:d}'"
关于windows - 使用 drawtext/start_number 跳过后显示视频的当前帧不评估任何变量，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43113742/