Well, I didn't solve the problem, but I found at least an explanation.
The video stream (duration=3176.106267) is shorter than the audio stream (duration=3221.490068). While the source video is in sync, the synchronization is lost during concatenation.
Is there any way to keep synchronization while concatenating videos? ffprobe input.mp4 -show_streams [STREAM] index=0 codec_name=h264 codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 profile=Main codec_type=video codec_time_base=1001/60000 codec_tag_string=avc1 codec_tag=0x31637661 width=1280 height=720 has_b_frames=2 sample_aspect_ratio=0:1 display_aspect_ratio=0:1 pix_fmt=yuv420p level=40 color_range=tv color_space=bt709 timecode=N/A id=N/A r_frame_rate=30000/1001 avg_frame_rate=30000/1001 time_base=1/90000 start_pts=0 start_time=0.000000 duration_ts=285849564 duration=3176.106267 bit_rate=69901 max_bit_rate=N/A nb_frames=95188 nb_read_frames=N/A nb_read_packets=N/A DISPOSITION:default=1 DISPOSITION:dub=0 DISPOSITION:original=0 DISPOSITION:comment=0 DISPOSITION:lyrics=0 DISPOSITION:karaoke=0 DISPOSITION:forced=0 DISPOSITION:hearing_impaired=0 DISPOSITION:visual_impaired=0 DISPOSITION:clean_effects=0 DISPOSITION:attached_pic=0 TAG:creation_time=2014-08-13 19:11:44 TAG:language=und TAG:encoder=JVT/AVC Coding [/STREAM] [STREAM] index=1 codec_name=aac codec_long_name=AAC (Advanced Audio Coding) profile=unknown codec_type=audio codec_time_base=1/44100 codec_tag_string=mp4a codec_tag=0x6134706d sample_fmt=fltp sample_rate=44100 channels=1 channel_layout=mono bits_per_sample=0 id=N/A r_frame_rate=0/0 avg_frame_rate=0/0 time_base=1/44100 start_pts=0 start_time=0.000000 duration_ts=142067712 duration=3221.490068 bit_rate=95966 max_bit_rate=N/A nb_frames=138738 nb_read_frames=N/A nb_read_packets=N/A DISPOSITION:default=1 DISPOSITION:dub=0 DISPOSITION:original=0 DISPOSITION:comment=0 DISPOSITION:lyrics=0 DISPOSITION:karaoke=0 DISPOSITION:forced=0 DISPOSITION:hearing_impaired=0 DISPOSITION:visual_impaired=0 DISPOSITION:clean_effects=0 DISPOSITION:attached_pic=0 TAG:creation_time=2014-08-13 19:11:44 TAG:language=und [/STREAM] Cheers, Marco _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user