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• Discord FFmpegPCMAudio bad audio quality

  17 mars 2021, par Yareyare

  I'm writing a discord music bot in python and encountered some audio quality issue. When I use discord.FFmpegPCMAudio("song.mp3") to play a mp3 file downloaded using youtube_dl in a channel, there're sometimes intermittent background noice and it sounds laggy and broken.
  
I tried to pass {'vbr':5} as an argument, and also tried discord.FFmpegOpusAudio, but doesn't do any better. The file itself is not corrupted, since it sounds normal when I play it using another app. Internet connection also isn't the cause, as each time I play the same file, the exact audio quality issue occurs at the exact same time.
  
I'm quite stuck right now. What other factors may caused this audio quality loss ?

  


• Emulate radio stream metadata

  17 juin 2018, par IllidanS4

  I work with an application that can connect to an audio stream via HTTP and play the audio. It can also connect to SHOUTcast and Icecast radios and play the streams, but for some radios, when the format is supported, it can read special metadata as well, like the name of the current song.

  I would like to use ffmpeg to produce an MP3 stream that contains the specific metadata this application understands. I know it is probably something specific to SHOUTcast or Icecast and not to the format itself, but I don’t know what exactly it is that the application can decode.

  If ffmpeg cannot produce such a stream (possibly because it is part of the HTTP metadata), I would welcome any details on how the metadata is encoded and how can I generate it (in PHP for example).

• Zlib vs. XZ on 2SF

  21 juillet 2012, par Multimedia Mike — General, psf, saltygme, xz, zlib

  I recently released my Game Music Appreciation website. It allows users to play an enormous range of video game music directly in their browsers. To do this, the site has to host the music. And since I’m a compression bore, I have to know how small I can practically make these music files. I already published the results of my effort to see if XZ could beat RAR (RAR won, but only slightly, and I still went with XZ for the project) on the corpus of Super Nintendo chiptune sets. Next is the corpus of Nintendo DS chiptunes.

  Repacking Nintendo DS 2SF
  The prevailing chiptune format for storing Nintendo DS songs is the .2sf format. This is a subtype of the Portable Sound Format (PSF). The designers had the foresight to build compression directly into the format. Much of payload data in a PSF file is compressed with zlib. Since I already incorporated Embedded XZ into the player project, I decided to try repacking the PSF payload data from zlib -> xz.

  In an effort to not corrupt standards too much, I changed the ’PSF’ file signature (seen in the first 3 bytes of a file) to ’psf’.

  Results
  There are about 900 Nintendo DS games currently represented in my website’s archive. Total size of the original PSF archive, payloads packed with zlib : 2.992 GB. Total size of the same archive with payloads packed as xz : 2.059 GB.

  Using xz vs. zlib saved me nearly a gigabyte of storage. That extra storage doesn’t really impact my hosting plan very much (I have 1/2 TB, which is why I’m so nonchalant about hosting the massive MPlayer Samples Archive). However, smaller individual files translates to a better user experience since the files are faster to download.

  Here is a pretty picture to illustrate the space savings :

  
  
  

  The blue occasionally appears to dip below the orange but the data indicates that xz is always more efficient than zlib. Here’s the raw data (comes in vanilla CSV flavor too).

  Interface Impact
  So the good news for the end user is that the songs are faster to load up front. The downside is that there can be a noticeable delay when changing tracks. Even though all songs are packaged into one file for download, and the entire file is downloaded before playback begins, each song is individually compressed. Thus, changing tracks triggers another decompression operation. I’m toying the possibility of some sort of background process that decompresses song (n+1) while playing song (n) in order to help compensate for this.

  I don’t like the idea of decompressing everything up front because A) it would take even longer to start playing ; and B) it would take a huge amount of memory.

  Corner Case
  There was at least one case in which I found zlib to be better than xz. It looks like zlib’s minimum block size is smaller than xz’s. I think I discovered xz to be unable to compress a few bytes to a block any smaller than about 60-64 bytes while zlib got it down into the teens. However, in those cases, it was more efficient to just leave the data uncompressed anyway.