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• avcodec/amrwbdec : Fix division by 0 in voice_factor()

  7 décembre 2017, par Michael Niedermayer

  avcodec/amrwbdec : Fix division by 0 in voice_factor()
  The added value matches "Digital cellular telecommunications system (Phase 2+) (GSM) ; Universal Mobile Telecommunications System (UMTS) ; LTE ; Extended Adaptive Multi-Rate - Wideband (AMR-WB+) codec ; Floating-point ANSI-C code (3GPP TS 26.304 version 14.0.0 Release 14)
  
  Extended Adaptive Multi-Rate - Wideband (AMR-WB+) codec ; Floating-point ANSI-C code"
  Fixes : runtime error : division by zero
  
  Fixes : 4415/clusterfuzz-testcase-minimized-4677752314658816
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/amrwbdec.c

• What is the best solution to convert old videos to newer more optimised formats ? [on hold]

  9 septembre 2019, par Jack

  Not too sure if this is the wrong place - please move it as I couldn’t find a more suitable network

  I have loads of media (Movies, TV Shows) as well as home videos (old VHS stuff ripped using some awful VHS to digital kit)

  Most of the movies/TV shows are in H264 (MP4/MKV containers) format, however some older ones are in AVI and WMV - I’d like to convert these into either H264 or a newer format (HEVC ?) To save some disk space and also because WMVs and AVIs are getting harder to deal with nowadays. I’m concerned about losing quality and am wondering what would be the best compromise in terms of converting these to HEVC/MPEG4’s encoder quality settings as compared to the data savings.

  The media collection of TV shows/movies, I don’t mind too much about losing some quality but the home videos/VHS tapes I have in old file formats, the storage factor for these is less important but I was wondering what I’d need to do to convert old AVI’s/MPEG2’s to MPEG4/HEVC - mainly if it is possible to convert one of these old video files to a newer format, without loss of quality, I thought the newer video encoding’s had lossless and lossy compression, but I could be completely wrong and don’t know much about video codecs.

  I was more curious on the best solution to do this as, Googling it gives me loads of commercial software and I’d rather have something which I can use command line/programmatically against my entire libraries. I also couldn’t find anything on these commercial sites about the technicals of re-encoding video so, was wondering if anyone had any experience with any command line applications/have an understanding of the video codecs.

• How do I decrypt the HLS stream to a .ts file when I have the key and IV ?

  28 décembre 2017, par A___ea_

  I have access to all the .ts files.
  My .m3u8 starts like this :

  #EXTM3U
  
  #EXT-X-VERSION:3
  
  #EXT-X-MEDIA-SEQUENCE:0
  
  #EXT-X-ALLOW-CACHE:YES
  
  #EXT-X-TARGETDURATION:13
  
  #EXT-X-KEY:METHOD=AES-128,URI="https://localserver/get_key?title_id=144", IV=0x4d1acfe1962002a4abedb8b68c65fa93
  
  #EXTINF:12.066667,
  
  1500_144_00000.ts
  
  #EXTINF:9.000000,
  
  1500_144_00001.ts
  
  EXTINF:9.000000,
  
  1500_144_00002.ts
  
  ...

  ... and the .m3u8 continues to show all the .ts files. It gives me the IV, and my Access key is f0d3321327cbaa1aa9ddba07801607442bebaad65b17ca75a15affd5

  No I’ve been searching my brain and the web for an answer on how to decrypt the .ts files (or the concatenated file) and I have seen suggestions using both openssl and ffmpeg but I can not seem to reach all the way with either tool.

  From what I’ve figured I can use the IV and Access_key to decrypt the stream using openssl. I have used the IV=4d1acfe1962002a4abedb8b68c65fa93 (removed 0x).

  I have so far tried to with the concatenated file :

  openssl aes-128-cbc -d -in concatenatedfile.ts -out decrypted_concatenatedfile.ts -nosalt -iv 4d1acfe1962002a4abedb8b68c65fa93 -K f0d3321327cbaa1aa9ddba07801607442bebaad65b17ca75a15affd5 

  But this just gives me

  bad decrypt
  
  139793444538016:error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt:evp_enc.c:539:

  I’ve seen suggestions that use a .key file and convert that to a readable format. But since I don’t have a .key file, but a ready string, I figure this is where I fail.

  I’ve tried using ffmpeg in accordance to this beautiful post by @aergistal.

  ffmpeg -i my.m3u8 -c copy output.ts

  But here too I seem to fail with my long string key.

  Any suggestions on how to proceed using openssl or ffmpeg are very welcome.

  Kindly