Serving a growing audio file with Django

Question

I would like to serve a growing audio file (raw PCM audio for now) with the possibility of seeking. I tried to manage it with Apache, but in the end wasn't able to achieve what I wanted.

Now I managed to come up with a solution within Django that seems to work quite nicely. Basically I created a view that delivers a part of the file and then sends a response with status code 206 and Content-Range header.

### DJANGO VIEW

MAX_CHUNK_SIZE = 32000
HEADER_PATH = "/path/to/header.wav"
MAX_WAV_LENGTH = 4294967303
BYTES_PER_SECOND = 32000

def get_audio(request, file_name):

    # get offset
    pos = int(request.GET.get("pos", 0))
    offset = pos * BYTES_PER_SECOND

    # get range
    r = request.META["HTTP_RANGE"]
    start = int(r.replace("bytes=", "").split("-")[0])
    start_o = start + offset

    # in case this is the first request, a wave header is added
    if start == 0:
        with open(HEADER_PATH, "rb") as f:
            data = f.read()
        length = 44
    else:
        data = ""
        length = 0
        start_o -= 44

    file_path = join(settings.STREAMS_DIR, file_name)

    # wait up to 10 seconds if the end of the file is reached
    # (in case it grows more)
    for _ in range(10):
        size = getsize(file_path)
        if size - start_o > 0:
            break
        else:
            sleep(1)

    length += min(MAX_CHUNK_SIZE, size - start_o)

    # if the length is zero (if end of file is reached and there is
    # nothing more to server), set the total length to the actual
    # served length
    if length == 0:
        total = size - offset + 44
    # else, set the total length to the maximum possible wav length
    # so that the browsers know that it has to send subsequent requests
    else:
        total = MAX_WAV_LENGTH

    # get the actual data from the raw audio file
    with open(file_path, "rb") as f:
        f.seek(start_o)
        data += f.read(length)

    # send response with use of Content-Range
    resp = HttpResponse(data, content_type="audio/x-wav", status=206)
    resp["Content-Range"] = "bytes " + str(start) + "-" + str(start + length) + "/" + str(total)
    return resp

In the browser, I can then simply request my audio like in the following way, to make it play from any point:

var fileName = "xyz.wav";
var start = 25; //seconds
audio = new Audio();
audio.src = "/getAudio/" + fileName + "?pos=" + start;
audio.play();

As I said, this all seems to work pretty well. But I would like to know this is a valid approach that I can use in production or if there are some major problems that I am not aware of.

Answer 1

• For large constants consider writing them as an expression and possibly comment on the size, just in case, to make it easier to understand.
• I'm not particularly fond of waiting for the file to grow, but I guess if it works it's fine.
• Serving static files is implemented in Django, including HTTP range parsing. However the one method I found only works in debug mode. Still, I'd try to reuse django.utils.http.parse_http_range and django.http.response.PartialHttpResponse if possible, so that not all of the data is read into memory at once.

Otherwise looks okay I'd say.