FFMpeg encoding not working on iPhone 3g but iPhone 4 is working well

I'm using the following code to encode video files for mobile devices. The problem is that video (mp4) is playing on iPhone 4 and Android devices well, but not working on iPhone 3g. Any ideas?

/usr/bin/ffmpeg -i <source> -vcodec libx264 -b 160k -bf 3 -b_strategy 1 -coder 1 -qmin 7 -qmax 30 -s 640x360 -sc_threshold 40 -flags +loop -cmp +chroma -me_range 16 -me_method hex -subq 5 -i_qfactor 0.71 -qcomp 0.75 -qdiff 4 -directpred 1 -flags2 +fastpskip -dts_delta_threshold 1 -acodec libfaac -ab 128k <output> -y 2> video_up/log/".$name开发者_StackOverflow社区.".txt > /dev/null 2>&1

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That’s too many flags. Try with -vcodec libx264, -vb 1000k, and -acodec libfaac and see if that plays (it should). Then you can try adding the rest to see which causes the problems.