I haven't tested it out, but I see an option in the man page to do:

ffmpeg -loglevel panic [rest of your ffmpeg stuff]

Should make it so only serious errors are logged, in theory

From the ffmpeg documentation:

’-report’
Dump full command line and log output to a file named program-YYYYMMDD-HHMMSS.log in the current directory. This file can be useful for bug reports. It also implies -loglevel debug.
Setting the environment variable FFREPORT to any value has the same effect.

Additional options are available to change the filename and verbosity.

https://ffmpeg.org/ffmpeg.html#Generic-options

subprocess.call docs says

To suppress stdout or stderr, supply a value of DEVNULL.

so you might replace

subprocess.call(['ffmpeg', '-i', songfile, songfile + ".ogg"])

using

subprocess.call(['ffmpeg', '-i', songfile, songfile + ".ogg"], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)

It has been 1 year and 8 months since you have asked this question, you might already have a solution for that. However, I found a solution to solve your problem.

You can solve this problem by modifying the original ffmpeg code when you package your python program.

First, find your ffmpeg lib folder, if you install with the default location, you can check your libs here: C:\Users\User\AppData\Local\Programs\Python\Python310\Lib\site-packages\ffmpeg.

Second, find _probe.py and modify codes, here is the code that already got modified, any change is written in the comments. You need to Popen add args: shell=True, stdin=subprocess.PIPE.

import json
import subprocess
from ._run import Error
from ._utils import convert_kwargs_to_cmd_line_args


def probe(filename, cmd='ffprobe', **kwargs):
    """Run ffprobe on the specified file and return a JSON representation of the output.

    Raises:
        :class:`ffmpeg.Error`: if ffprobe returns a non-zero exit code,
        an :class:`Error` is returned with a generic error message.
        The stderr output can be retrieved by accessing the
        ``stderr`` property of the exception.
    """
    args = [cmd, '-show_format', '-show_streams', '-of', 'json']
    args += convert_kwargs_to_cmd_line_args(kwargs)
    args += [filename]

    # Original: p = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    # Popen add args: shell=True, stdin=subprocess.PIPE,

    p = subprocess.Popen(args, shell=True, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = p.communicate()
    if p.returncode != 0:
        raise Error('ffprobe', out, err)
    return json.loads(out.decode('utf-8'))


__all__ = ['probe']

Then, go to _run.py. You need to add shell=True, modify stdin=subprocess.PIPE or modify pipe_stdin=True (The code section below is just a part of the code):

@output_operator()
def run_async(
    stream_spec,
    cmd='ffmpeg',
    pipe_stdin=False,
    pipe_stdout=False,
    pipe_stderr=False,
    quiet=False,
    overwrite_output=False,
):
    """Asynchronously invoke ffmpeg for the supplied node graph.

Args:
    pipe_stdin: if True, connect pipe to subprocess stdin (to be
        used with ``pipe:`` ffmpeg inputs).
    pipe_stdout: if True, connect pipe to subprocess stdout (to be
        used with ``pipe:`` ffmpeg outputs).
    pipe_stderr: if True, connect pipe to subprocess stderr.
    quiet: shorthand for setting ``capture_stdout`` and
        ``capture_stderr``.
    **kwargs: keyword-arguments passed to ``get_args()`` (e.g.
        ``overwrite_output=True``).

Returns:
    A `subprocess Popen`_ object representing the child process.

Examples:
    Run and stream input::

        process = (
            ffmpeg
            .input('pipe:', format='rawvideo', pix_fmt='rgb24', s='{}x{}'.format(width, height))
            .output(out_filename, pix_fmt='yuv420p')
            .overwrite_output()
            .run_async(pipe_stdin=True)
        )
        process.communicate(input=input_data)

    Run and capture output::

        process = (
            ffmpeg
            .input(in_filename)
            .output('pipe':, format='rawvideo', pix_fmt='rgb24')
            .run_async(pipe_stdout=True, pipe_stderr=True)
        )
        out, err = process.communicate()

    Process video frame-by-frame using numpy::

        process1 = (
            ffmpeg
            .input(in_filename)
            .output('pipe:', format='rawvideo', pix_fmt='rgb24')
            .run_async(pipe_stdout=True)
        )

        process2 = (
            ffmpeg
            .input('pipe:', format='rawvideo', pix_fmt='rgb24', s='{}x{}'.format(width, height))
            .output(out_filename, pix_fmt='yuv420p')
            .overwrite_output()
            .run_async(pipe_stdin=True)
        )

        while True:
            in_bytes = process1.stdout.read(width * height * 3)
            if not in_bytes:
                break
            in_frame = (
                np
                .frombuffer(in_bytes, np.uint8)
                .reshape([height, width, 3])
            )
            out_frame = in_frame * 0.3
            process2.stdin.write(
                frame
                .astype(np.uint8)
                .tobytes()
            )

        process2.stdin.close()
        process1.wait()
        process2.wait()

.. _subprocess Popen: https://docs.python.org/3/library/subprocess.html#popen-objects
"""
    args = compile(stream_spec, cmd, overwrite_output=overwrite_output)
    stdin_stream = subprocess.PIPE if pipe_stdin else None
    stdout_stream = subprocess.PIPE if pipe_stdout or quiet else None
    stderr_stream = subprocess.PIPE if pipe_stderr or quiet else None

    # Original: return subprocess.Popen(
    #           args, stdin=pipe_stdin, stdout=stdout_stream, stderr=stderr_stream)    
    # Add shell=True, modify stdin=subprocess.PIPE or modify pipe_stdin=True

    return subprocess.Popen(
        args, shell=True, stdin=subprocess.PIPE, stdout=stdout_stream, stderr=stderr_stream
    )

AFAIK there is no way, loglevel is no use. Look at ffmpeg.c:

init_opts();
show_banner();

and cmdutils.c:

void show_banner(void)
{
    fprintf(stderr, "%s version " FFMPEG_VERSION ", Copyright (c) %d-%d the FFmpeg developers\n",
            program_name, program_birth_year, this_year);
    fprintf(stderr, "  built on %s %s with %s %s\n",
            __DATE__, __TIME__, CC_TYPE, CC_VERSION);
    fprintf(stderr, "  configuration: " FFMPEG_CONFIGURATION "\n");
    print_all_libs_info(stderr, INDENT|SHOW_CONFIG);
    print_all_libs_info(stderr, INDENT|SHOW_VERSION);
}

See here for an unsuccessful attempt of skipping it (I don't get what the GPL has to do with anything of this). I suggest you to file a bug and hope you are convicing enough.

As many others, I have ffmpeg compiled with show_banner() commented out, it's simply tiresome.

Hello you can set those env variable:

export OPENCV_VIDEOIO_DEBUG=1
export OPENCV_FFMPEG_DEBUG=1
export OPENCV_LOG_LEVEL=DEBUG