From ecb8f3c2b4e282d5ef416516bcbfb92821f06bf6 Mon Sep 17 00:00:00 2001 From: Daniel Bevenius Date: Wed, 18 Jun 2025 17:41:43 +0200 Subject: [PATCH] examples : add stereo to mono conversion in read_audio_data (#3266) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit This commit adds a conversion from stereo to mono in the `read_audio_data` function of `common-whisper.cpp`. The motivation for this change is prior to Commit 7d3da68f792018e81a758881e081154d1cbe6b6f ("examples : use miniaudio for direct decoding flac, mp3, ogg and wav (#2759)", there was a step that read stereo int16 data -> pcm16 (448512 samples), and then converted to mono (224256 samples), and then also convert to stereo in `pcmf32s. The middle step here seems to have been missed when rewriting the code to use Miniaudio and caused issues then transcribing stereo audio files. For example, currently using the audio sample in the linked issue the output is: ```console [00:00:00.000 --> 00:00:03.000] (speaker 1) Sous-titres réalisés para la communauté d'Amara.org ``` And with the change in this commit the output is: ``` [00:00:00.000 --> 00:00:01.500] (speaker 1) *sonnerie de téléphone* [00:00:01.500 --> 00:00:07.000] (speaker 1) Salut jeune homme ! [00:00:07.000 --> 00:00:08.500] (speaker 0) C'est vrai que je te dérange ? [00:00:08.500 --> 00:00:10.500] (speaker 1) Ah pas du tout, pas du tout, pas du tout ! [00:00:10.500 --> 00:00:12.500] (speaker 1) J'étais en train de... [00:00:12.500 --> 00:00:14.500] (speaker 1) de préparer un courrier ``` Resolves: https://github.com/ggml-org/whisper.cpp/issues/3092 --- examples/common-whisper.cpp | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/examples/common-whisper.cpp b/examples/common-whisper.cpp index 8b9229ed..6218a882 100644 --- a/examples/common-whisper.cpp +++ b/examples/common-whisper.cpp @@ -112,13 +112,20 @@ bool read_audio_data(const std::string & fname, std::vector& pcmf32, std: } if (stereo) { - pcmf32s.resize(2); - pcmf32s[0].resize(frame_count); - pcmf32s[1].resize(frame_count); - for (uint64_t i = 0; i < frame_count; i++) { - pcmf32s[0][i] = pcmf32[2*i]; - pcmf32s[1][i] = pcmf32[2*i + 1]; - } + std::vector stereo_data = pcmf32; + pcmf32.resize(frame_count); + + for (uint64_t i = 0; i < frame_count; i++) { + pcmf32[i] = (stereo_data[2*i] + stereo_data[2*i + 1]); + } + + pcmf32s.resize(2); + pcmf32s[0].resize(frame_count); + pcmf32s[1].resize(frame_count); + for (uint64_t i = 0; i < frame_count; i++) { + pcmf32s[0][i] = stereo_data[2*i]; + pcmf32s[1][i] = stereo_data[2*i + 1]; + } } ma_decoder_uninit(&decoder);