Google Speech-to-Text's 10 MB local limit and a 16 kHz mono Sume WAV

Google Cloud Speech-to-Text accepts about one minute of audio on a synchronous request and up to 10 MB for local files. Asynchronous requests run to about 480 minutes, still with 10 MB for local files, with no limit for Cloud Storage URIs. A 16 kHz mono wav from Sume audio detach is about 1.92 MB a minute by arithmetic, so 10 MB holds roughly five minutes.

Google's figures are from its Speech-to-Text quotas page, read 2026-10-03. Sume's format options are from audio detach.

What the quotas say

The page splits limits by request type.

Arithmetic for a Sume wav

Sume's default detach output is pcm_s16le: 16 bits is 2 bytes a sample. At sample_rate 16000 and mono, that is 32000 bytes a second, so 60 seconds is 1.92 MB and 300 seconds is 9.6 MB. This is general PCM arithmetic, not a figure from either vendor, and WAV headers add a few bytes.

Sume's maximum detach output is 900 seconds, which would be about 28.8 MB, so a full-length detach is three times too large for a local Google request. Take a range of 300 seconds or less, or send the file by Cloud Storage.

Detaching a minute for the sync call

Use range: { start, end } with a gap of 60 seconds or less. Keep channels at mono and sample_rate at 16000. Each job costs $0.01 and returns an audio_url on media.sume.com plus duration_seconds and source_duration_seconds.

Detach works only on media.sume.com sources, so the video must already be an artifact or asset in your workspace.

• start past the source end fails detach_start_past_source.
• A range longer than 900 s fails audio_detach_range_empty.
• A video with no audio fails detach_source_has_no_audio.

When to use Cloud Storage instead

For a recording of an hour or more, the 10 MB local limit is the wrong path. Google's page says Cloud Storage URIs have no size limit on asynchronous requests, so upload the audio there and reference it. For Sume, anything over 30 minutes of source video is beyond the 1800 second source cap anyway.

Checking the numbers yourself

Download the detach result and read its byte size, then compare with Google's limit. The docs give a header size for neither side, and Google's page does not say whether MB means decimal or binary megabytes, so leave a margin of a few percent.

If you detach in 300 second ranges, each file is near the limit, so use 240 seconds for a safer margin.

A worked example

Take a 20 minute video. Detach it in ranges of 240 seconds, giving five files of about 7.7 MB each by the arithmetic above, each under the 10 MB local limit. Five jobs cost $0.05 at Sume's $0.01 per job.

Or upload the whole audio to Cloud Storage and use one asynchronous request, which Google says has no size limit for Storage URIs. That route needs a Google Cloud account and a bucket, but avoids the splitting.