Hi all,
I have cross-compilled ffmpeg 3.1.3 + mpd for openwrt, the ARCH of target board is MIPS. the MCU of target board is MT7688, it doesn't have FPU,DSP. (mpd is a music play daemon which uses ffmpeg library as backend for music play.) it works well for mp3. however,while I try to play aac/m4a codec audio network steams, the default aac decoder doesn't works well, it will docode audio to noises, you can't hear even a bit original music. and the CPU usage is nearly 100%. For comparison, I compiled ffmpeg3.1.3+mpd for X86 PC, and play the same aac/mp4 network steams, it works well.
through trial and error, I found one non-perfect remedy: that is use aac decoder "aac_fixed" instead of "aac". using this decoder, although the decoded sound have background noise, however, you can hear the original music from the background noise. and the CPU usage is low(20% only).
After browsing the code , I guess this phenomenon is because default aac codec use float point manipulation, which will consume much more cpu cycles in comparison with aac_fixed, which uses integer manipulation.
as I said, it is an non-perfect remedy, because the background noise is large, but how to eliminate the background noise for the board, I have no idea, is there any workaround for this? any help will be appreciated, thanks in advance.
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