Split Audio by File Size Using Ecasound

This article explains whether Ecasound can automatically split audio recordings when reaching specific file size limits, highlights native limitations, and provides practical workarounds. While Ecasound lacks a dedicated, built-in trigger to split files strictly by byte size, you can achieve this behavior by calculating time-based thresholds or piping raw audio streams to external Linux command-line utilities.

Native Capability

Ecasound does not include a direct parameter to monitor file size on disk and rotate files automatically once a megabyte or gigabyte threshold is crossed. Its output modules are designed to write continuous streams to files, devices, or standard output until manually interrupted or until a preset time limit is reached.

Method 1: Converting Size Limits to Time Limits

For uncompressed audio (such as standard WAV or raw PCM), file size is directly proportional to time. You can compute the exact duration required to reach a specific file size using the audio format parameters:

\[\text{Bytes per Second} = \text{Sample Rate} \times \text{Number of Channels} \times \left(\frac{\text{Bit Depth}}{8}\right)\]

For example, recording CD-quality audio (44.1 kHz, 16-bit, stereo) generates:

\[44,100 \times 2 \times 2 = 176,400\text{ bytes per second (approx. 10.58 MB per minute)}\]

If you want to split files at roughly 500 MB:

\[\frac{500,000,000}{176,400} \approx 2,834\text{ seconds}\]

You can then run Ecasound with the -t (time limit) flag inside a shell loop to create sequentially numbered files:

count=1
while true; do
  ecasound -i:alsa -f:16,2,44100 -o:"recording_$count.wav" -t:2834
  ((count++))
done

Method 2: Piping to the split Utility

If your workflow requires strict byte-level splitting, you can route Ecasound's output to stdout in raw format and pipe it into the GNU split utility.

ecasound -i:alsa -f:s16_le,2,44100 -o:stdout | split -b 500M -d - "part_"

• -b 500M instructs the split command to cut the incoming raw stream precisely every 500 megabytes.
• Note that cutting raw audio directly will produce headerless PCM chunks. To play them back, specify the raw parameters (-f:s16_le,2,44100) or manually convert the chunks back into valid WAV containers with utilities like sox or ffmpeg.

Method 3: Scripting via Ecasound Control Interface (ECI)

For complex setups, Ecasound provides an interactive mode and control interface (ECI) usable via Python, Perl, or C. A script can continuously check the size of the target recording file using system calls. When the file reaches the threshold, the script issues an engine stop command, reconfigures the output target to a new filename, and restarts recording with minimal latency.