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FFMPEG - 缩放视频过滤器未提供预期结果

发布于 2024-12-12 19:35:57 字数 3326 浏览 0 评论 0原文

如果有人问这个问题，我们深表歉意。我找不到它，但如果找到了，请告诉我，我会关闭它。

我正在尝试对原始尺寸为 480x360、目标尺寸为 400x300 的视频进行简单缩放。视频以 FLV 形式开始，最终需要以 MPEG 形式结束。我使用以下命令行来执行此操作：

ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg

当我在 MPEG Streamclip 中播放缩放视频时，比例是正确的，并且视频信息显示尺寸为 400x300。但是，当我在 Quicktime 中播放缩放后的视频时，视频会缩放至 478x359。更重要的是，FFMPEG 本身将视频视为 478x359，因此以后对其执行的任何命令（修剪、转换、叠加等）都会生成 478x359 的视频。

最初的工作流程需要将 FLV 转换为 MPEG，但我尝试过使用几种不同的输入和输出格式（FLV -> FLV、FLV -> MPEG、MPEG -> MPEG 等），但结果均相同。不过，只要我最终能得到 MPEG，我就可以处理实现此缩放工作所需的许多步骤和转换。

如果您愿意，我将在下面粘贴命令行输出，并且下面还链接了示例输入视频。非常感谢您的帮助。

http://www.monkeydriver.com/dpassera/stack_flv.zip

命令行输出：

ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg

ffmpeg version 0.7-rc1, Copyright (c) 2000-2011 the FFmpeg developers
  built on May 21 2011 22:13:19 with gcc 4.1.2 20080704 (Red Hat 4.1.2-50)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 
 --mandir=/usr/share/man --incdir=/usr/include --disable-avisynth
 --extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
 -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC'
 --enable-avfilter --enable-libdirac --enable-libgsm --enable-libmp3lame
 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264
 --enable-gpl --enable-postproc --enable-pthreads --enable-shared
 --enable-swscale --enable-vdpau --enable-version3 --enable-x11grab
 --disable-yasm --enable-filters --enable-filter=movie

  libavutil    50. 40. 1 / 50. 40. 1
  libavcodec   52.120. 0 / 52.120. 0
  libavformat  52.108. 0 / 52.108. 0
  libavdevice  52.  4. 0 / 52.  4. 0
  libavfilter   1. 77. 0 /  1. 77. 0
  libswscale    0. 13. 0 /  0. 13. 0
  libpostproc  51.  2. 0 / 51.  2. 0

[flv @ 0x11dd3b30] Estimating duration from bitrate, this may be inaccurate
Input #0, flv, from 'user.flv':

  Metadata:
    duration        : 5
    videocodecid    : 2
    audiocodecid    : 6
    canSeekToEnd    : true
    createdby       : FMS 4.0
    creationdate    : Mon Oct 31 11:43:44 2011

  Duration: 00:00:04.62, start: 0.000000, bitrate: N/A
    Stream #0.0: Video: flv, yuv420p, 640x480, 1k tbr, 1k tbn, 1k tbc
    Stream #0.1: Audio: nellymoser, 44100 Hz, mono, s16

[buffer @ 0x11ddc950] w:640 h:480 pixfmt:yuv420p

[scale @ 0x11dda610] w:640 h:480 fmt:yuv420p -> w:400 h:300 fmt:yuv420p flags:0xa0000004

[mpeg @ 0x11dd6bd0] VBV buffer size not set, muxing may fail

Output #0, mpeg, to 'user_scaled.mpg':
  Metadata:
    duration        : 5
    videocodecid    : 2
    audiocodecid    : 6
    canSeekToEnd    : true
    createdby       : FMS 4.0
    creationdate    : Mon Oct 31 11:43:44 2011
    encoder         : Lavf52.108.0

    Stream #0.0: Video: mpeg1video, yuv420p, 400x300, q=2-31, 200 kb/s, 90k tbn, 60 tbc

    Stream #0.1: Audio: mp2, 44100 Hz, mono, s16, 64 kb/s

Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1

Press [q] to stop encoding
frame=  230 fps=  0 q=10.2 size=     366kB time=3.82 bitrate= 785.6kbits/s dup=175 drop=0 
frame=  267 fps=  0 q=10.7 Lsize=     412kB time=4.43 bitrate= 761.3kbits/s dup=203 drop=0    

video:370kB audio:36kB global headers:0kB muxing overhead 1.568959%
原文

Apologies if this question has been asked. I couldn't find it, but if it has, please let me know and I'll close this out.

I'm attempting a simple scale of a video whose original dimensions are 480x360 and whose target dimensions are 400x300. The video starts as an FLV and eventually needs to end up as an MPEG. I'm using the following command line to do this:

ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg

When I play the scaled video in MPEG Streamclip, the scale is correct and the video info shows that the dimensions are 400x300. However, when I play the scaled video in Quicktime, the video is scaled to 478x359. More importantly, FFMPEG, itself, treats the video as being 478x359, so any future commands (trimming, conversion, overlaying, etc) executed on it result in a video of 478x359.

The initial workflow required an FLV to MPEG conversion, but I've tried this with several different in and out formats (FLV -> FLV, FLV -> MPEG, MPEG -> MPEG, etc) all with the same results. As long as I can end up with an MPEG, though, I can deal with however many steps and conversions it would take to get this scaling working.

I'll paste the command-line output below, and a sample input video is also linked below, if you'd like it. Thank you very much for any help.

http://www.monkeydriver.com/dpassera/stack_flv.zip

Command-line output:

ffmpeg -i user.flv -vf "scale=400:300" user_scaled.mpg

ffmpeg version 0.7-rc1, Copyright (c) 2000-2011 the FFmpeg developers
  built on May 21 2011 22:13:19 with gcc 4.1.2 20080704 (Red Hat 4.1.2-50)
  configuration: --prefix=/usr --libdir=/usr/lib64 --shlibdir=/usr/lib64 
 --mandir=/usr/share/man --incdir=/usr/include --disable-avisynth
 --extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
 -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -fPIC'
 --enable-avfilter --enable-libdirac --enable-libgsm --enable-libmp3lame
 --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libx264
 --enable-gpl --enable-postproc --enable-pthreads --enable-shared
 --enable-swscale --enable-vdpau --enable-version3 --enable-x11grab
 --disable-yasm --enable-filters --enable-filter=movie

  libavutil    50. 40. 1 / 50. 40. 1
  libavcodec   52.120. 0 / 52.120. 0
  libavformat  52.108. 0 / 52.108. 0
  libavdevice  52.  4. 0 / 52.  4. 0
  libavfilter   1. 77. 0 /  1. 77. 0
  libswscale    0. 13. 0 /  0. 13. 0
  libpostproc  51.  2. 0 / 51.  2. 0

[flv @ 0x11dd3b30] Estimating duration from bitrate, this may be inaccurate
Input #0, flv, from 'user.flv':

  Metadata:
    duration        : 5
    videocodecid    : 2
    audiocodecid    : 6
    canSeekToEnd    : true
    createdby       : FMS 4.0
    creationdate    : Mon Oct 31 11:43:44 2011

  Duration: 00:00:04.62, start: 0.000000, bitrate: N/A
    Stream #0.0: Video: flv, yuv420p, 640x480, 1k tbr, 1k tbn, 1k tbc
    Stream #0.1: Audio: nellymoser, 44100 Hz, mono, s16

[buffer @ 0x11ddc950] w:640 h:480 pixfmt:yuv420p

[scale @ 0x11dda610] w:640 h:480 fmt:yuv420p -> w:400 h:300 fmt:yuv420p flags:0xa0000004

[mpeg @ 0x11dd6bd0] VBV buffer size not set, muxing may fail

Output #0, mpeg, to 'user_scaled.mpg':
  Metadata:
    duration        : 5
    videocodecid    : 2
    audiocodecid    : 6
    canSeekToEnd    : true
    createdby       : FMS 4.0
    creationdate    : Mon Oct 31 11:43:44 2011
    encoder         : Lavf52.108.0

    Stream #0.0: Video: mpeg1video, yuv420p, 400x300, q=2-31, 200 kb/s, 90k tbn, 60 tbc

    Stream #0.1: Audio: mp2, 44100 Hz, mono, s16, 64 kb/s

Stream mapping:
Stream #0.0 -> #0.0
Stream #0.1 -> #0.1

Press [q] to stop encoding
frame=  230 fps=  0 q=10.2 size=     366kB time=3.82 bitrate= 785.6kbits/s dup=175 drop=0 
frame=  267 fps=  0 q=10.7 Lsize=     412kB time=4.43 bitrate= 761.3kbits/s dup=203 drop=0    

video:370kB audio:36kB global headers:0kB muxing overhead 1.568959%

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半世蒼涼 2024-12-19 19:35:57

咬牙切齿之后，我认为这个问题与ffmpeg无关，而与Quicktime有关。

Quicktime Player (10.1 (501.5)) 会缩放视频以匹配窗口大小，并具有最小窗口大小。因此，无论实际视频大小如何，Quicktime 都会将其缩放到至少 480 x 360。这就是为什么信息显示在“格式”部分（真实大小）中包含大小信息，但也有“当前大小”部分。更改窗口大小会更改后一个数字。

因此，使用 ffmpeg 缩放视频时可以使用 -vf scale 或仅使用 -s，但不要相信 Quicktime Player 会以正确的尺寸向您显示它们。我推荐 VLC 作为一个非常强大的替代方案。

After much gnashing of teeth, I think the problem has nothing to do with ffmpeg, and everything to do with Quicktime.

Quicktime Player (10.1 (501.5)) scales videos to match the size of the window, and has a minimum window size. So regardless of the actual video size, Quicktime will scale it to at least 480 by 360. This is why the info display has size information in the "Format" section (the true size), but also has a "Current Size" section. Changing the window size changes that latter number.

So, scale videos using ffmpeg either with -vf scale or just -s, but don't trust Quicktime Player to show them to you at the correct size. I recommend VLC as a very capable alternative.

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