Convert MP3 bitrate from a stream into another stream with ffmpeg
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03-07-2021 - |
Question
Using ffmpeg, I would like to know if it's possible to convert mp3 bitrate as data chunks are received?
That means I would send slowly chunks to ffmpeg so that it outputs a mp3 with another bitrate.
So in very-pseudo-code, it looks like it:
MP3 Request from user
Send the default mp3 to ffmpeg with parameters to convert to the desired bitrate.
As it's writing a new file, write what as been writen so far in the Response outputstream (I'm in ASP.Net)
Is that feasable or I need to switch to another technology?
[EDIT]
For now, I'm trying a solution like this: Convert wma stream to mp3 stream with C# and ffmpeg
[EDIT 2]
I answered my question, and it is feasible with an url as input and standard output as output. Using an url allows to process a file chunk by chunk, and using stdout, we can access data while it is processed.
Solution
Here is the method in C#, read on http://jesal.us/2008/04/how-to-manipulate-video-in-net-using-ffmpeg-updated/ and changed to work from stream to stream. That means "Live" conversion of streams with ffmpeg.
The '-' at the ends of the command stands for "Standard Output", so that's why it's the destination.
private void ConvertVideo(string srcURL)
{
string ffmpegURL = @"C:\ffmpeg.exe";
DirectoryInfo directoryInfo = new DirectoryInfo(@"C:\");
ProcessStartInfo startInfo = new ProcessStartInfo();
startInfo.FileName = ffmpegURL;
startInfo.Arguments = string.Format("-i \"{0}\" -ar 44100 -f mp3 -", srcURL);
startInfo.WorkingDirectory = directoryInfo.FullName;
startInfo.UseShellExecute = false;
startInfo.RedirectStandardOutput = true;
startInfo.RedirectStandardInput = true;
startInfo.RedirectStandardError = true;
startInfo.CreateNoWindow = false;
startInfo.WindowStyle = ProcessWindowStyle.Normal;
using (Process process = new Process())
{
process.StartInfo = startInfo;
process.EnableRaisingEvents = true;
process.ErrorDataReceived += new DataReceivedEventHandler(process_ErrorDataReceived);
process.OutputDataReceived += new DataReceivedEventHandler(process_OutputDataReceived);
process.Exited += new EventHandler(process_Exited);
try
{
process.Start();
process.BeginErrorReadLine();
process.BeginOutputReadLine();
process.WaitForExit();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
finally
{
process.ErrorDataReceived -= new DataReceivedEventHandler(process_ErrorDataReceived);
process.OutputDataReceived -= new DataReceivedEventHandler(process_OutputDataReceived);
process.Exited -= new EventHandler(process_Exited);
}
}
}
void process_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
if (e.Data != null)
{
byte[] b = System.Text.Encoding.Unicode.GetBytes(e.Data);
// If you are in ASP.Net, you do a
// Response.OutputStream.Write(b)
// to send the converted stream as a response
}
}
void process_Exited(object sender, EventArgs e)
{
// Conversion is finished.
// In ASP.Net, do a Response.End() here.
}