CODEWITHSUNDEEP
ffmpeg
M.Yazdian
M.Yazdian

Reputation: 59

ffmpeg says "at least one output file must be specified" when piping from another process

To force ffmpeg to read, decode, and scale only once in order to bring CPU usage down I put those steps in one ffmpeg process and piped the result into another ffmpeg process that performed the encoding.

This improved the overall processing time by 15–20%.

INPUT_STREAM="ffmpeg -i $INPUT_FILE -vf scale=720:-1,crop=720:400 -threads auto -f yuv4mpegpipe -"

$INPUT_STREAM | ffmpeg -y -f yuv4mpegpipe -i - \
$AUDIO_OPTIONS_P2 $VIDEO_OPTIONS_P2 -b:v 250k -threads auto out-250.mp4 \
$AUDIO_OPTIONS_P2 $VIDEO_OPTIONS_P2 -b:v 500k -threads auto out-500.mp4 \
$AUDIO_OPTIONS_P2 $VIDEO_OPTIONS_P2 -b:v 700k -threads auto out-700.mp4

I then tried the syntax below:

 ffmpeg -i c:\sample.mp4 -threads auto -f yuv4mpegpipe - |  ffmpeg -y -f yuv4mpegpipe -i -vcodec libx264 -b:v 250k -threads auto c:\out-250.mp4 -vcodec libx264 -b:v 260k -threads auto c:\out-260.mp4

… but this error appears:

At least one output file must be specified

But I have specified the out put file which is: C:\out-260.mp4. Still it doesn't work

What's wrong?

Upvotes: 0

Views: 6169

Answers (1)

slhck
slhck

Reputation: 38672

 ffmpeg -y -f yuv4mpegpipe -i -vcodec …

You didn't specify any input file. To read from stdin, use -:

ffmpeg -y -f yuv4mpegpipe -i - -vcodec …

Upvotes: 1

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