Concat MP4 files using AnnexB bitstream format

concat-mp4-annexb.md

Concat MP4 files without transcoding to mpeg

1. Use the h264_mp4toannexb bitstream filter to convert the mp4s (video steam only) into the AnnexB bitstream format

   ffmpeg -i input1.mp4 -vcodec copy -vbsf h264_mp4toannexb -acodec copy part1.ts
   # repeat for up to inputN
   

2. Concat the files using cat

   cat part1.ts part2.ts > parts.ts
   

3. Remux the files into a complete mp4

   ffmpeg -y -i parts.ts -acodec copy -absf aac_adtstoasc parts.mp4
   

test_mp4_concat.sh

#!/bin/sh

FFMPEG=../ffmpeg-all

$FFMPEG -y -i input1.mp4 -vcodec copy -vbsf h264_mp4toannexb -acodec copy part1.ts
$FFMPEG -y -i input2.mp4 -vcodec copy -vbsf h264_mp4toannexb -acodec copy part2.ts
cat part1.ts part2.ts > parts.ts
$FFMPEG -y -i parts.ts -acodec copy -absf aac_adtstoasc parts.mp4

test_mpeg_concat.sh

#!/bin/sh

FFMPEG=../ffmpeg-all

$FFMPEG -y -i input1.mp4 -f mpeg input1.mpg
$FFMPEG -y -i input2.mp4 -f mpeg input2.mpg
cat input1.mpg input2.mpg > full.mpg
$FFMPEG -y -i full.mpg -b:v 1500k -s 720x480 -vcodec libx264 -acodec aac -ac 2 -b:a 96k -f mp4 -strict experimental output.mp4

with android I had to add a -vcodec copy flag to the final command so it would not try to convert codec "h264" to "libx264"

$FFMPEG -y -i parts.ts -vcodec copy -acodec copy -absf aac_adtstoasc parts.mp4

it works and its very fast!!!