I've run into some strange problems with kdenlive 0.8. I use it to process vids from my HD cam, and I'm used to preprocess the vids first (especially resize to the target HD480 resolution). But now I get a lot of strange issues with the audio when working with the clip in kdenlive:

ALSA lib pcm.c:7245:(snd_pcm_recover) underrun occured

ALSA lib pcm.c:7245:(snd_pcm_recover) underrun occured

ALSA lib pcm.c:7245:(snd_pcm_recover) underrun occured

and the sound is distorted. This happens only with the recoded clips, which is done like this:

ffmpeg -i HDV_0024.MP4 -pass 1 -threads 2 -r 50 -s hd480 -vcodec mpeg2video -b 3M -acodec libmp3lame -ab 128000 -ac 1 -ar 22050 -threads 2 -y work/HDV_0024.MP4

ffmpeg -i HDV_0024.MP4 -pass 2 -threads 2 -r 50 -s hd480 -vcodec mpeg2video -b 3M -acodec libmp3lame -ab 128000 -ac 1 -ar 22050 -threads 2 -y work/HDV_0024.MP4

With mplayer the clips play just fine. With the original clip (or even with '-acodec copy') everything works.

Not sure if this is kdenlive issue ...

I tested your command line, and for me when I play the result with ffplay, the sound plays high-pitched. When I play with melt, the sound is distorted. Both ffplay and melt indicate there are 2 audio channels even though -ac 1. It seems the problem is somewhere in ffmpeg. -ac 2 fixes it.