python-telegram-bot send_voice sends empty file

Question

I am trying to send a voice message using a local OGG file. The voice message is sent but when trying to play the file in telegram it seems empty. Any idea why ? Here is the code I'm using :

async def audio_received(update: Update, context: ContextTypes.DEFAULT_TYPE):
    await context.bot.send_voice(
        chat_id=update.effective_chat.id, voice=open("sample-3.ogg", "rb")
    )

if __name__ == "__main__":
    application = (
        ApplicationBuilder()
        .token("MY_TOKEN")
        .build()
    )
    audio_handler = MessageHandler(filters.VOICE, audio_received)
    application.add_handler(audio_handler)
    application.run_polling()

Thanks a lot for your help!

Answer 1

As per Telegram's documentation on sendVoice, the audio files should satisfy the following:

• be an .ogg file,
• be encoded with OPUS,
• have a size below 50MB (could change), and,
• according to this answer, have a bitrate from 32kb to 64kb.

Since you mentioned that the encoding might have solved this issue, I will take the answer again from this answer:

async def audio_received(update: Update, context: ContextTypes.DEFAULT_TYPE):
    # ffmpeg -i sample-3.ogg -loglevel panic \
    #        -c:a libopus -b:a 32k -vbr on \
    #        -compression_level 10 -frame_duration 60 -application voip \
    #        output.ogg
    subprocess.run([
        'ffmpeg', '-i', 'sample-3.ogg', '-loglevel', 'panic',
        '-c:a', 'libopus', '-b:a', '32k', '-vbr', 'on',
        '-compression_level', '10', '-frame_duration', '60', '-application', 'voip',
        'output.ogg', '-y' # -y confirms overriding files with the same name
    ])
    await context.bot.send_voice(
        chat_id=update.effective_chat.id, voice=open("output.ogg", "rb")
    )