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• How to encode specific metadata version in FFMPEG ?

  11 février 2021, par Charlie Britton

  I am batch converting lots of songs into shorter "Advert" songs for SHOUTcast and to be recognised as adverts by the server. The song must have ":Advert" for both the title and the artist metadata tags. When I use the following command :

  



  ffmpeg -i "$i" -c copy -vn -map_metadata -1 -metadata title=":Advert" -metadata artist=":Advert" -t 120 "adverts/ADVERT_$i"


  



  I would expect it to output the song with only ":Advert" as title and artist metadata but when I import it into the radio playout software (using ID3 1.x tagging) the metadata has not copied across and is therefore lost. Output from ffmpeg :

  



  ffmpeg version 3.0.2 Copyright (c) 2000-2016 the FFmpeg developers
  built with Apple LLVM version 9.0.0 (clang-900.0.37)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/3.0.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --disable-lzma --enable-vda
  libavutil      55. 17.103 / 55. 17.103
  libavcodec     57. 24.102 / 57. 24.102
  libavformat    57. 25.100 / 57. 25.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 31.100 /  6. 31.100
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[mp3 @ 0x7feba6800000] Skipping 0 bytes of junk at 230934.
[mjpeg @ 0x7feba7000600] Changing bps to 8
Input #0, mp3, from 'Joakim Karud - Vibe With Me.mp3':
  Metadata:
    major_brand     : dash
    minor_version   : 0
    compatible_brands: iso6mp41
    encoder         : Lavf56.40.101
    artist          : Joakim Karud
    title           : Vibe With Me
  Duration: 00:02:53.06, start: 0.025056, bitrate: 138 kb/s
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, s16p, 128 kb/s
    Metadata:
      encoder         : Lavc56.60
    Stream #0:1: Video: mjpeg, yuvj420p(pc, bt470bg/unknown/unknown), 1280x720 [SAR 1:1 DAR 16:9], 90k tbr, 90k tbn, 90k tbc
    Metadata:
      comment         : Cover (front)
Output #0, mp3, to 'adverts/ADVERT_Joakim Karud - Vibe With Me.mp3':
  Metadata:
    TIT2            : :Advert
    TPE1            : :Advert
    TSSE            : Lavf57.25.100
    Stream #0:0: Audio: mp3, 44100 Hz, stereo, 128 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
size=    1876kB time=00:02:00.00 bitrate= 128.1kbits/s speed=1.44e+03x
video:0kB audio:1876kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.024837%


  



  I believe this is happening because the tag names are different (e.g. title should be title, but is TIT2 when output. Please could someone specify how I could ensure that the metadata is encoded in the ID3 1.x format so that it is readable by the radio playout software. Many thanks.

  


• 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.

• Seamlessly switching from streaming one video to another

  28 octobre 2018, par mustang

  Suppose I have two videos :

  Video A is of a ball going through one full cycle of a bounce and is 30 frames long. At frame 1, the ball is at the top. On frame 15, the ball hits the floor, and on frame 30 the ball is back up at the same position as it started (suppose zero energy loss).

  Video B is of the same ball drifting to the right and it is 30 frames long too. At frame 1, the ball is in the same position as it is in Video A. On frame 15, it is half way to the right and down. n frame 30, it is all the way right and on the ground.

  I want a way to stream video A indefinitely. Then, when some event occurs, I want to be able to wait until video A is on frame 1 and seamlessly change over to streaming video B. How would I perform that ?