使用 drawtext/start_number 跳过后显示视频的当前帧，不评估任何变量

Question

我想在使用 ffplay 播放视频时显示当前帧数。我已经看过 this 解决方案，但是当我搜索视频的任何部分时，计数器会重置。有一个变量 start_number，ffplay 文档说它是 The starting frame number for the n/frame_num variable. The default value is "0". 似乎在开始视频或在 I 帧之间寻找时 n 设置为那个。我认为将此变量设置为 %{floor(t*60)} 可以解决我的问题，但在运行之后：

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 赋值中的任何变量都会引发此错误。我不知道我的语法是否正确，但这是否意味着它不计算表达式？或者它可能出于某种原因不接受变量？

在那次失败之后，我尝试将文本设置为 %{t}，它播放了视频，但反复出现此错误并且左上角没有文本：

[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？
有没有另一种方法可以将当前帧写入视频甚至控制台window?

此时使用 Windows 10 Enterprise 和最新版本的 ffplay for windows。

Answer 1

假设视频帧速率恒定为 60 fps，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}'"

使用 drawtext/start_number 跳过后显示视频的当前帧，不评估任何变量

Displaying the current frame of a video after skipping using drawtext/start_number not evaluation any variables

windows

video

ffmpeg

drawtext