Is the STM32C55 powerful enough to decode audio?

[peregrin]

Hello,

I am making a device which will play encoded audio files from a (Q)SPI flash and I wanted to use the STM32C55 (with its internal DAC). Alas, I haven’t been able to find flash/RAM/CPU frequency requirements for the codecs except for MP3 Helix (https://github.com/liuduanfei/helix), but I would rather use Opus because it has a better bitrate-to-quality ratio.

Does anyone have experience with decoding audio on the STM32C55 (or any similar MCU for that matter)? How much flash and RAM was needed for the decoder?

Thanks.

[Khaled_DHIF]

Hello @peregrin,

Yes, the STM32C5 is a reasonable platform for audio decoding. The Cortex-M33 should be capable of handling this type of workload, depending on the codec and the efficiency of the decoder implementation.

That said, actual feasibility will depend on several factors beyond the MCU itself, including the codec/library used, PCM buffer size, stack usage, any RTOS overhead, and other application logic running alongside playback.

In general, MP3 is usually easier to fit on a small MCU, while Opus offers better compression but typically requires more flash, RAM, and CPU. If Opus is your preferred choice, I would recommend validating it early on the target hardware.

For the best chance of success, I would start with a simple setup:

• mono
• moderate sample rate, such as 16 kHz or 24 kHz
• fixed-point decoder if available
• DMA-based DAC output
• double-buffered PCM
• minimal background tasks

I should add that I do not have exact footprint metrics for the decoder on this platform, so the most reliable approach is to benchmark it directly on the target hardware and confirm the available CPU and RAM headroom for your configuration.

Kind regards,
DHIF Khaled

[AScha.3]

Hi,

i made an audio player on H743 , so i can tell , what it needs about :

• i used MINIMP3 , in float , for optimum precision/sound (look on git)
• needs about 10KB RAM, 40K flash ; ( decoder about 8K )
• speed , clocks : about 6ms for 40ms audio(stereo 44k1/16b), so about 30 Mips for decoder
• + some 16 KB RAM for buffers, for inbuf and outbuf (DMA to DACs)

Your cpu at 144M could do it at about 20% cpu load, i guess . My H743 at 200M has about 15% load.

And always optimizer at -O2 ! ..or -Ofast , otherwise no fun !!

btw

I had it at first on a F411 , at 100M core , needed about 30..40% cpu, (same, float in stereo)

plays from SD-card.

And about quality: at 128kb , almost CD quality; most CDs are so bad recorded, you can hear no difference; at 320kb anyway same , the quality of the original source is more important.