FFMPEG: MP4 videos are not playing properly in iPhone, iPod, iPad

Question

I am converting videos from m4v, flv to MP4 for iPhone, iPod, iPad.

I am using the below command to convert these videos

ffmpeg -y -i video_1336500693.m4v -vcodec libx264 -vpre slow -vpre ipod640 -b 250k -bt 50k -acodec libfaac -ab 56k -ac 2 -s 480x320 video_1336500693.mp4

The video part of this mp4 file is working fine but the audio is not working properly. I am using HTML5 for this.

The audio works for first 8-10 seconds but after that audio does not work and the strange thing is if I jump to forward or backward the audio works.

Can anyone suggest what's going wrong?

Answer 1

Slight modification to the command did the job. I added -ar 48000 and it worked

ffmpeg -y -i video_1336500693.m4v -vcodec libx264 -vpre slow -vpre ipod640 -b 250k -bt 50k -acodec libfaac -ac 2 -ar 48000 -ab 64k -s 480x320 video_1336500693.mp4