[FFmpeg-trac] #10523(undetermined:new): Artifacts converting aac to wav

FFmpeg trac at avcodec.org
Thu Aug 17 05:41:27 EEST 2023 

#10523: Artifacts converting aac to wav
-------------------------------------+-------------------------------------
             Reporter:  drive4code   |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:               |                  Version:  4.3.6
  undetermined                       |
             Keywords:  ffmpeg       |               Blocked By:
  conversion                         |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 == Summary of the bug
 Anytime You convert an AAC to WAV (pcm_s24le; the 16 bit version...) you
 get artifacts in random spots trough the video, which can get better or
 worse as you run the program again

 == What you were trying to accomplish
 Convert a 32 bit 48000 kHz 1080p 60fps .mp4 AAC video using  into a 24 bit
 44100 kHz .wav WAV audio

 I should mention i tried to convert it to several other formats, and
 because i found the same artifacts in all of them I assume it's a problem
 with all conversions of this type

 == The problem you encountered
 There are artifacts at random points towards the video. Here's the best
 way  to describe them after visualizing the audio:

 They seem to fall in the distortion artifacts category. Some waves (seems
 like half the time for a short period of time) over-extend over the voice
 of the speaker, causing the artifacts. It sounds like a robotic sound
 overextending the speaker.

 == How to reproduce:
 Run the command below on a file according to spec, make it large enough
 (10-20 minutes) to scroll through it and find the mention artifacts

 I can also provide an example on request

 {{{
 % ffmpeg -y -i "$vid" -vn -c:a pcm_s24le -ar 44100 -ac 2 $audio
 ffmpeg version n4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
 built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
 }}}

 == The output provided by ffmpeg -v 9 -loglevel 99 -i (would be too big to
 fit)

 ...
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231133, offset e148f8da, dts 236680192, size 326, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231134, offset e1492afb, dts 236681216, size 359, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231135, offset e149a267, dts 236682240, size 326, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231136, offset e149aac4, dts 236683264, size 346, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231137, offset e14a0c19, dts 236684288, size 328, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231138, offset e14a248e, dts 236685312, size 333, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231139, offset e14a56b6, dts 236686336, size 360, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231140, offset e14a9f3e, dts 236687360, size 331, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] AVIndex stream 1, sample
 231141, offset e14aebf9, dts 236688384, size 309, distance 0, keyframe 1
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] Processing st: 1, edit list 0 -
 media time: 1024, duration: 236688000
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] drop a frame at curr_cts: 0 @ 0
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'udta' parent:'moov' sz:
 333 8697198 8697523
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'meta' parent:'udta' sz:
 325 8 325
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'hdlr' parent:'meta' sz:
 33 8 313
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] ctype=[0][0][0][0]
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stype=mdir
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'ilst' parent:'meta' sz:
 280 41 313
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'[169]nam' parent:'ilst'
 sz: 80 8 272
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'[169]ART' parent:'ilst'
 sz: 33 88 272
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'[169]day' parent:'ilst'
 sz: 28 121 272
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'[169]too' parent:'ilst'
 sz: 36 149 272
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] type:'[169]cmt' parent:'ilst'
 sz: 95 185 272
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] on_parse_exit_offset=3788499620
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] rfps: 60.000000 0.000265
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] rfps: 120.000000 0.001061
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] rfps: 240.000000 0.004244
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] rfps: 59.940060 0.001057
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] Before
 avformat_find_stream_info() pos: 3788499620 bytes read:8730299 seeks:1
 nb_streams:2
 [h264 @ 0x557ed98411c0] nal_unit_type: 7(SPS), nal_ref_idc: 3
 [h264 @ 0x557ed98411c0] nal_unit_type: 8(PPS), nal_ref_idc: 3
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stream 0, sample 0, dts -18000
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stream 1, sample 0, dts -21333
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] demuxer injecting skip 1024 /
 discard 0
 [aac @ 0x557ed9842800] skip 1024 / discard 0 samples due to side data
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stream 0, sample 0, dts -18000
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stream 1, sample 1, dts 0
 [h264 @ 0x557ed98411c0] nal_unit_type: 9(AUD), nal_ref_idc: 0
 [h264 @ 0x557ed98411c0] nal_unit_type: 7(SPS), nal_ref_idc: 3
 [h264 @ 0x557ed98411c0] nal_unit_type: 8(PPS), nal_ref_idc: 3
 [h264 @ 0x557ed98411c0] nal_unit_type: 6(SEI), nal_ref_idc: 0
     Last message repeated 1 times
 [h264 @ 0x557ed98411c0] nal_unit_type: 5(IDR), nal_ref_idc: 3
 [h264 @ 0x557ed98411c0] Format yuv420p chosen by get_format().
 [h264 @ 0x557ed98411c0] Reinit context to 1920x1088, pix_fmt: yuv420p
 [h264 @ 0x557ed98411c0] ct_type:0 pic_struct:0
 [h264 @ 0x557ed98411c0] no picture
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] All info found
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stream 0: start_time: 0.015
 duration: 4931.03
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] stream 1: start_time: 0
 duration: 4931
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] format: start_time: 0 duration:
 4931.08 (estimate from stream) bitrate=6146 kb/s
 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x557ed983f440] After
 avformat_find_stream_info() pos: 118453 bytes read:8848704 seeks:2
 frames:2
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10523>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker

More information about the FFmpeg-trac mailing list