[FFmpeg-user] encode results with incorrect duration & start values

Lou lou at lrcd.com
Wed Sep 16 20:20:07 CEST 2015

On Wed, 16 Sep 2015 11:33:29 -0400
dean lewis <deanlewis at fastmail.com> wrote:

> FFmpeg version 2.7.2 (09.08.2015)
> OS X 10.10.5 (14F27)
> Mac Pro (Late 2013)
> We have 6 videos from FCP, exported as ProRes files, that need to be concatenated.
> Step one was to first encode each of the videos into H.264:

If you want to concatenate ProRes why are you encoding to H.264?

> [code]/Users/robodean/Desktop/ffmpeg/ffmpeg -i ch01b_t-m-pack.mov -map 0:0 -map 0:1 -c:a aac -cutoff 15000 -ab 320k -strict -2 -async 1 -c:v libx264 -crf 20 -r 23.98 -s 960x540 -aspect 16:9 -pix_fmt yuv420p -profile:v high -partitions partb8x8+partp4x4+partp8x8+parti8x8 -b-pyramid 1 -weightb 1 -8x8dct 1 -fast-pskip 1 -coder ac -trellis 1 -me_method hex -flags +loop -sws_flags fast_bilinear -direct-pred 1 -sc_threshold 40 -qmin 3 -qmax 51 -qdiff 4 -threads 12 -sn -y ch01b_t-m-pack.mp4
> [/code]

Complete console output is missing. You need to show the full command
and complete console output for each step so the issue can be attemped
to be duplicated.

Why do you not use the x264 encoding presets (-preset option) instead
of listing a horde of options.

Why did you use "-async 1"?

> But when we concatenated the files using ffmpeg and compared it to a
> reference concatenation exported from FCP, we found that there were
> numerous "offsets" in the in points of the videos in the final output.

How did you concatenate the videos?

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