使用 ffmpeg 和 xfade 过滤器合并多个视频文件

Question

我需要将多个视频文件（包含音频）合并为一个视频。我注意到 xfade 最近发布并使用了它，但我运行遇到了音频同步问题。

所有视频的视频和音频格式/分辨率/声望和比特率/等都相同。

这是我用来合并 5 个不同持续时间的视频和 0.5 交叉淡入淡出过渡的方法：

ffmpeg \
-i v0.mp4 \
-i v1.mp4 \
-i v2.mp4 \
-i v3.mp4 \
-i v4.mp4 \
-filter_complex \
"[0][1]xfade=transition=fade:duration=0.5:offset=3.5[V01]; \
 [V01][2]xfade=transition=fade:duration=0.5:offset=32.75[V02]; \
 [V02][3]xfade=transition=fade:duration=0.5:offset=67.75[V03]; \
 [V03][4]xfade=transition=fade:duration=0.5:offset=98.75[video]; \
 [0:a][1:a]acrossfade=d=0.5:c1=tri:c2=tri[A01]; \
 [A01][2:a]acrossfade=d=0.5:c1=tri:c2=tri[A02]; \
 [A02][3:a]acrossfade=d=0.5:c1=tri:c2=tri[A03]; \
 [A03][4:a]acrossfade=d=0.5:c1=tri:c2=tri[audio]" \
-vsync 0 -map "[video]" -map "[audio]" out.mp4

上面的代码生成了一个带音频的视频。第一和第二段与音频对齐，但从第二个过渡开始，声音未对齐。

Answer 1

您的偏移量不正确。尝试：

ffmpeg -i v0.mp4 -i v1.mp4 -i v2.mp4 -i v3.mp4 -i v4.mp4 -filter_complex \
"[0][1:v]xfade=transition=fade:duration=1:offset=3[vfade1]; \
 [vfade1][2:v]xfade=transition=fade:duration=1:offset=10[vfade2]; \
 [vfade2][3:v]xfade=transition=fade:duration=1:offset=21[vfade3]; \
 [vfade3][4:v]xfade=transition=fade:duration=1:offset=25,format=yuv420p; \
 [0:a][1:a]acrossfade=d=1[afade1]; \
 [afade1][2:a]acrossfade=d=1[afade2]; \
 [afade2][3:a]acrossfade=d=1[afade3]; \
 [afade3][4:a]acrossfade=d=1" \
-movflags +faststart out.mp4

如何获取 xfade offset 值：

input	input duration	+	previous xfade `offset`	-	xfade `duration`	`offset` =
`v0.mp4`	4	+	0	-	1	3
`v1.mp4`	8	+	3	-	1	10
`v2.mp4`	12	+	10	-	1	21
`v3.mp4`	5	+	21	-	1	25

_{这些是简化的示例持续时间，与原始问题中显示的持续时间不同。}

有关详细信息，请参阅 xfade and acrossfade 过滤器文档。
有关过渡效果和更多示例的图库，请参阅 FFmpeg Wiki: xfade。
你可以get input durations with ffprobe.

Answer 2

自动化该过程将有助于处理计算偏移量时的错误。我创建了一个 Python 脚本，用于计算并为任何大小的输入视频列表构建图表：

https://gist.github.com/royshil/369e175960718b5a03e40f279b131788

它将检查视频文件的长度（ffprobe）以找出正确的偏移量。

问题的症结在于构建过滤图和计算偏移量：

# Prepare the filter graph
video_fades = ""
audio_fades = ""
last_fade_output = "0:v"
last_audio_output = "0:a"
video_length = 0
for i in range(len(segments) - 1):
    # Video graph: chain the xfade operator together
    video_length += file_lengths[i]
    next_fade_output = "v%d%d" % (i, i + 1)
    video_fades += "[%s][%d:v]xfade=duration=0.5:offset=%.3f[%s]; " % \
        (last_fade_output, i + 1, video_length - 1, next_fade_output)
    last_fade_output = next_fade_output

    # Audio graph:
    next_audio_output = "a%d%d" % (i, i + 1)
    audio_fades += "[%s][%d:a]acrossfade=d=1[%s]%s " % \
        (last_audio_output, i + 1, next_audio_output, ";" if (i+1) < len(segments)-1 else "")
    last_audio_output = next_audio_output

它可能会产生一个过滤图，例如

[0:v][1:v]xfade=duration=0.5:offset=42.511[v01]; 
[v01][2:v]xfade=duration=0.5:offset=908.517[v12]; 
[v12][3:v]xfade=duration=0.5:offset=1098.523[v23]; 
[v23][4:v]xfade=duration=0.5:offset=1234.523[v34]; 
[v34][5:v]xfade=duration=0.5:offset=2375.523[v45]; 
[v45][6:v]xfade=duration=0.5:offset=2472.526[v56]; 
[v56][7:v]xfade=duration=0.5:offset=2659.693[v67]; 
[0:a][1:a]acrossfade=d=1[a01]; 
[a01][2:a]acrossfade=d=1[a12]; 
[a12][3:a]acrossfade=d=1[a23]; 
[a23][4:a]acrossfade=d=1[a34]; 
[a34][5:a]acrossfade=d=1[a45]; 
[a45][6:a]acrossfade=d=1[a56]; 
[a56][7:a]acrossfade=d=1[a67]

Answer 3

上面的Python脚本对我帮助很大，但是在计算偏移量时出错了。视频流应为 'video_length - fade_duration*(i+1)'.

如下代码：

def gen_filter(segments):
    video_fades = ""
    audio_fades = ""
    settb = ""
    last_fade_output = "0:v"
    last_audio_output = "0:a"
    fade_duration = 0.3

    video_length = 0
    file_lengths = [0]*len(segments)
    
    for i in range(len(segments)):
        settb += "[%d]settb=AVTB[%d:v];" % (i,i)

    for i in range(len(segments)-1):

        file_lengths[i] = float(ffmpeg.probe(segments[i])['format']['duration'])

        video_length += file_lengths[i]
        next_fade_output = "v%d%d" % (i, i + 1)
        video_fades += "[%s][%d:v]xfade=transition=fade:duration=%f:offset=%f%s%s" % \
            (last_fade_output, i + 1, fade_duration, video_length - fade_duration*(i+1), '['+next_fade_output+'];' if (i) < len(segments)-2 else "","" if (i) < len(segments)-2 else ",format=yuv420p[video];")
        last_fade_output = next_fade_output

        next_audio_output = "a%d%d" % (i, i + 1)
        audio_fades += "[%s][%d:a]acrossfade=d=%f%s" % \
            (last_audio_output, i + 1, fade_duration*2, '['+next_audio_output+'];' if (i) < len(segments)-2 else "[audio]")
        last_audio_output = next_audio_output
        
    return settb + video_fades + audio_fades

Answer 4

has a mistake, which was pointed out by 中的脚本，但显示为新定义。

如果有人只想要上一个答案的更正原始脚本，请将 # Prepare the filter graph 之后的块替换为：

# Prepare the filter graph
video_fades = ""
audio_fades = ""
last_fade_output = "0:v"
last_audio_output = "0:a"
video_length = 0
fade_duration = 0.5

for i in range(len(segments) - 1):
    # Video graph: chain the xfade operator together
    video_length += file_lengths[i]
    next_fade_output = "v%d%d" % (i, i + 1)
    video_fades += "[%s][%d:v]xfade=duration=0.5:offset=%.3f[%s]; " % \
        (last_fade_output, i + 1, video_length - fade_duration*(i+1), next_fade_output)
    last_fade_output = next_fade_output

    # Audio graph:
    next_audio_output = "a%d%d" % (i, i + 1)
    audio_fades += "[%s][%d:a]acrossfade=d=1[%s]%s " % \
        (last_audio_output, i + 1, next_audio_output, ";" if (i+1) < len(segments)-1 else "")
    last_audio_output = next_audio_output

# Assemble the FFMPEG command arguments
ffmpeg_args = ['ffmpeg',
               *itertools.chain(*files_input),
               '-filter_complex', video_fades + audio_fades,
               '-map', '[%s]' % last_fade_output,
               '-map', '[%s]' % last_audio_output,
               '-y',
               args.output_filename]

# Run FFMPEG
subprocess.run(ffmpeg_args)

Answer 5

我写了一个similar but simpler script:

#!/bin/bash
# usage: ls -1 something*.mp4 | ffmpeg_xfade.sh output.mp4

fdur=0.5
ftrans=pixelize
f0n=0
f1n=1
alld=0

while read f; do
    allvf="$allvf$vf"
    allaf="$allaf$af"
    inputs="$inputs -i $f "
    d=$(ffprobe -v error -select_streams v:0 -show_entries stream=duration -of default=noprint_wrappers=1:nokey=1 "$f")
    alld=$(bc -l <<< "$alld + $d")
    offset=$(bc -l <<< "$alld - $fdur * $f1n")
    vf="[vfade$f0n][$f1n:v]xfade=transition=$ftrans:duration=$fdur:offset=$offset[vfade$f1n];"
    af="[afade$f0n][$f1n:a]acrossfade=d=$fdur[afade$f1n];"
    (( f0n++ ))
    (( f1n++ ))
done

f0n=$(( f0n - 1 ))
allvf="[0:v]copy[vfade0];$allvf[vfade$f0n]format=yuv420p"
allaf="[0:a]acopy[afade0];$allaf[afade$f0n]acopy"

#set -vx
ffmpeg -y -hide_banner $inputs \
    -filter_complex "$allvf;$allaf" \
    -c:v h264_nvenc -preset p7 -profile:v high -rc-lookahead 8 -spatial_aq 1 -pix_fmt yuv420p \
    -c:a libopus \
    ""

由此产生的 ffmpeg 命令类似于：

ffmpeg -y -hide_banner  -i f1.mp4  -i f2.mp4 -i f3.mp4  -i f4.mp4         
-filter_complex "[0:v]copy[vfade0];[vfade0][1:v]xfade=transition=pixelize:duration=0.5:offset=-.5[vfade1];
[vfade1][2:v]xfade=transition=pixelize:duration=0.5:offset=10.0[vfade2];
[vfade2][3:v]xfade=transition=pixelize:duration=0.5:offset=20.0[vfade3];
[vfade3]format=yuv420p;
[0:a]acopy[afade0];[afade0][1:a]acrossfade=d=0.5[afade1];
[afade1][2:a]acrossfade=d=0.5[afade2];
[afade2][3:a]acrossfade=d=0.5[afade3];
[afade3]acopy"       -c:v h264_nvenc -preset p7 -profile:v high -rc-lookahead 8 -spatial_aq 1 -pix_fmt yuv420p -c:a libopus "output.mp4"

使用 ffmpeg 和 xfade 过滤器合并多个视频文件

Merging multiple video files with ffmpeg and xfade filter

video

ffmpeg

concatenation

cross-fade