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• How to download a part of mp3 from server ?

  20 août 2020, par Sharukh Mohammed

  Use Case

  


  My use case is roughly equal to, adding a 15-second mp3 file to a 1 min video. All transcoding merging part will be done by FFmpeg-android so that's not the concern right now.

  


  The flow is as follows

  


  

  • User can select any 15 seconds (ExoPlayer-streaming) of an mp3 (considering 192Kbps/44.1KHz of 3mins = up to 7MB)

  


  • Then download ONLY the 15 second part and add it to the video's audio stream. (using FFmpeg)

  


  • Use the obtained output

  


  


  Tried solutions

  


  


  • Extracting fragment of audio from a url

    


    RANGE_REQUEST - I have replicated the exact same algorithm/formula in Kotlin using the exact sample file provided. But the output is not accurate (± 1.5 secs * c) where c is proportional to startTime

    


  


  • How to crop a mp3 from x to x+n using ffmpeg ?

    


    FFMPEG_SS - This works flawlessly with remote URLs as input, but there are two downsides,

    


    

    1. as startTime increases, the size of downloaded bytes are closer to the actual size of the mp3.

    


    2. ffmpeg-android does not support network requests module (at least the way we complied)

    


    


  


  


  So above two solutions have not been fruitful and currently, I am downloading the whole file and trimming it locally, which is definitely a bad UX.
I wonder how Instagram's music addition to story feature works because that's close to what I wanted to implement.

  


• FFMPEG Compile Custom

  14 décembre 2016, par Madskillz RCE

  I need to compile FFMPEG with version 2.1.8 of source and with the following options -

  ./configure --arch=x86 --target-os=mingw32 --cross-prefix=i686-w64-mingw32- --cc=i686-w64-mingw32-gcc --disable-postproc --enable-shared --disable-static --disable-decoder=libvpx --disable-encoder=aac --enable-avisynth --enable-gpl --enable-version3 --enable-pthreads --enable-avfilter --enable-runtime-cpudetect --enable-nonfree --pkg-config=pkg-config --enable-libquvi --enable-libfaac --enable-libnut --enable-libgsm --enable-libfreetype --enable-libvorbis --enable-libspeex --enable-libmp3lame --enable-zlib --enable-libtheora --enable-bzlib --enable-libvpx --enable-libxvid --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libschroedinger --enable-librtmp --enable-libass --enable-libx264 --enable-libbluray --enable-openssl --enable-libflite --enable-libsox --disable-ffplay --enable-libcdio --enable-libcelt --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libxavs --disable-outdev=sdl --disable-muxers --enable-muxer=encx --extra-cflags=-I/usr/i686-mingw32/include --extra-ldflags=-L/usr/i686-mingw32/lib --extra-libs='-lx264 -lpthread -lwinmm -llua -liconv -lcurl -lws2_32 -lssl -lcrypto -lwldap32 -lgdi32 -lwsock32' 

  I need to know on which system will be good to compile this ?

  also some libraries might be obsolete so where can I find them ?

  Please provide your input how would you compile it ?

  The configuration was extracted from a custom version of avcodec-55.dll , need to demux a video using new compiled ffmpeg.

  Regards

• ffmpeg download mp3 in chunks slower than whole file

  6 août 2021, par loretoparisi

  I'm programmatically downloading in Python mp3 file's as wav chunks, seeking at position with ss and t with ffmpeg resulting in a sequence of ffmpeg commands

  


  ffmpeg -i https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_5MG.mp3 -acodec pcm_s16le -ac 1 -ar 44100 -ss 0:08:55.780000 -t 0:01:00.000000 -sn -vn -y -f wav pipe:1
ffmpeg -i https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_5MG.mp3 -acodec pcm_s16le -ac 1 -ar 44100 -ss -ss 0:09:55.780000 -t 0:01:00.000000 -sn -vn -y -f wav pipe:1
ffmpeg -i https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_5MG.mp3 -acodec pcm_s16le -ac 1 -ar 44100 -ss -ss -ss 0:10:55.780000 -t 0:01:00.000000 -sn -vn -y -f wav pipe:1
...


  


  executed via concurrent.futures.ThreadPoolExecutor in this way :

  


  with concurrent.futures.ThreadPoolExecutor(max_workers=NTHREADS) as executor:
        for i,cmd in enumerate(process_list):
            futures.append(executor.submit(downloader.chunk_download,(cmd,i)))

        for future in concurrent.futures.as_completed(futures):
            try:
                completed.append(future.result())
            except Exception as e:print(e)
    completed.sort() 
    for k,c in enumerate(completed):
        if not k:
            waveform = c[1]
        else:
            waveform = np.append(waveform,c[1])


  


  where chunk_download is concat the chunks into the whole waveform

  


  def chunk_download(self,args):
        cmd=args[0]
        i=args[1]
        print('Downloading chunk n° %i' % i)

        print( ' '.join(cmd))
        process = subprocess.run(cmd,
                            stdout=subprocess.PIPE,
                            stderr=subprocess.PIPE,
                            bufsize=10**8)
        #buffer, stderr = process.communicate()
        buffer = process.stdout
        stderr = process.stderr
        print('chunk n° %i DOWNLOADED' % i)
        # convert to signal
        chunk_waveform = np.frombuffer(buffer=buffer, dtype=np.uint16, offset=8*44)
        chunk_waveform = chunk_waveform.astype(self.dtype)  
        print(len(chunk_waveform)/44100) 

        return i,chunk_waveform


  


  this works ok, but if I download the whole mp3, executing the command in cmd like :

  


  ffmpeg -i https://file-examples-com.github.io/uploads/2017/11/file_example_MP3_5MG.mp3 -acodec pcm_s16le -ac 1 -ar 44100 -sn -vn -y -f wav pipe:1


  


  It will take less time than the concurrent chunks download for the same file length, while I would expect the opposite. Could be this related to ffmpeg threading option (param --thread ?). If not, why the concurrent chunks download operation is slower ?