mplayer doesn't like popen suddenly? - c++

Question

Been stumped over a problem with popen for a few days.
The code:
int main(){
FILE *fp = popen("mplayer /home/linaro/Music/cp.mp3", "r");
char buffer[1028];
while (fgets(buffer, 1028, fp) != NULL)
{
std::cerr<<buffer;
}
pclose(fp);
fp = 0;
return 0;
}
was run at the shop on a linaro embedded controller. Ran fine, no errors. Even though the code is simple (Just plays a coldplay song on execution and then quits) it seems to be causing me more grief than one would think.
If I copy and paste the command itself into a normal bash shell, it runs fine. And what's worse, is it ran fine up until it got plugged in somewhere else. I'm not sure if it is now being connected to via a headphone jack versus before it was in a line out jack.
Regardless, the error I get when I run it is (summarized down to the relevant part)
MPlayer svn r34540 (Ubuntu), built with gcc-4.6 (C) 2000-2012 MPlaye4
Team mplayer: could not connect to socket mplayer: No such file or
directory Failed to open LIRC support. You will not be able to use
your remote control.
Playing /home/linaro/Music/cp.mp3 libavformat version 53.21.1
(external) Mismatching header version 53.19.0 Audio only file format
detected. Clip info: Title: The Scientist Artist: Coldplay Album: A
Rush Of Blood To The Head Year: 2002 Comment: Genre: Unknown Load
subtitles in /home/linaro/Music/ Requested audio codec family [mpg123]
(afm=mpg123) not available. Enable it at compilation. Opening audio
decoder: [ffmpeg] FFmpeg/libavcodec audio decoders libavcodec version
53.35.0 (external) Mismatching header version 53.32.2 AUDIO: 44100 Hz, 2
ch, floatle, 256.0 kbit/9.07% (ratio: 32002->352800) Selected audio
codec: [ffmp3float] afm: ffmpeg (FFmpeg MPEG layer-3 audio) Home
directory not accessible: Permission denied AO: [pulse] Init failed:
Connection refused Failed to initialize audio driver 'pulse' Home
directory not accessible: Permission denied [AO_ALSA] alsa-lib:
pcm_hw.c:1293:(snd_pcm_hw_open) open '/dev/snd/pcmC1D0p' failed (-22):
Invalid argument [AO_ALSA] Playback open error: Invalid argument
Failed to initialize audio driver 'alsa' [AO SDL] Samplerate: 44100Hz
Channels: Stereo Format floatle [AO SDL] using aalib audio driver. [AO
SDL] Unsupported audio format: 0x1d. [AO SDL] Unable to open audio: No
available audio device Failed to initialize audio driver 'sdl:aalib'
Could not open/initialize audio device -> no sound. Audio: no sound
Video: no video
Again, if I copy and paste the exact command it executes via popen into the console, it begins playing. It fails if pass -ao alsa, -ao pulse, -ao oss as well, which has me completely stumped. Any help would be appreciated!
Edit:
Linux is linaro, based on Ubuntu 12.04 using arm CPU

Answer 1

Issue wound up being as Jonas and alk suggested -- permissions. Something along the way changed how it ran, but at the end of the day the dirty fix was to just include
su - user -c ' mplayer ... '
To the line being called.