[FFmpeg-trac] #7273(ffmpeg:open): Exported AAC does not work properly

[FFmpeg]

#7273: Exported AAC does not work properly
----------------------------------------+----------------------------------
             Reporter:  DriverX         |                    Owner:  (none)
                 Type:  defect          |                   Status:  open
             Priority:  important       |                Component:  ffmpeg
              Version:  4.0.6           |               Resolution:
             Keywords:  aac regression  |               Blocked By:
             Blocking:                  |  Reproduced by developer:  0
Analyzed by developer:  0               |
----------------------------------------+----------------------------------
Changes (by juanitogan):

 * version:  unspecified => 4.0.6
 * component:  undetermined => ffmpeg

Comment:

 Still having this issue in ffmpeg 5.0.

 It appears that regardless of how I produce an AAC with 5.1 channels of
 FL+FR+FC+LFE+SL+SR, ffprobe always reports `channel_layout=unknown` like
 so:

 {{{
 [STREAM]
 index=1
 codec_name=aac
 codec_long_name=AAC (Advanced Audio Coding)
 profile=LC
 codec_type=audio
 codec_tag_string=[0][0][0][0]
 codec_tag=0x0000
 sample_fmt=fltp
 sample_rate=48000
 channels=6
 channel_layout=unknown
 bits_per_sample=0
 id=N/A
 r_frame_rate=0/0
 avg_frame_rate=0/0
 time_base=1/1000
 start_pts=0
 start_time=0.000000
 duration_ts=N/A
 duration=N/A
 bit_rate=N/A
 max_bit_rate=N/A
 bits_per_raw_sample=N/A
 nb_frames=N/A
 nb_read_frames=N/A
 nb_read_packets=N/A
 extradata_size=26
 DISPOSITION:default=1
 DISPOSITION:dub=0
 DISPOSITION:original=0
 DISPOSITION:comment=0
 DISPOSITION:lyrics=0
 DISPOSITION:karaoke=0
 DISPOSITION:forced=0
 DISPOSITION:hearing_impaired=0
 DISPOSITION:visual_impaired=0
 DISPOSITION:clean_effects=0
 DISPOSITION:attached_pic=0
 DISPOSITION:timed_thumbnails=0
 DISPOSITION:captions=0
 DISPOSITION:descriptions=0
 DISPOSITION:metadata=0
 DISPOSITION:dependent=0
 DISPOSITION:still_image=0
 TAG:language=eng
 TAG:ENCODER=Lavc59.18.100 aac
 TAG:DURATION=00:01:00.021000000
 [/STREAM]
 }}}

 I've tried all sorts of workarounds including:

 `-channel_layout "5.1(side)"`
 `-channel_layout FL+FR+FC+LFE+SL+SR`
 `-channel_layout 1551`
 `-af "channelmap=`
 `-af "channelmap=map=`
 `-af "aformat=channel_layouts=`
 `-filter_complex
 "channelsplit=channel_layout=5.1[FL][FR][FC][LFE][BL][BR];[FL][FR][FC][BL][BR][LFE]join=inputs=6:channel_layout=1551:map=0.0-FL|1.0-FR|2.0-FC|3.0-SL|4.0-SR|5.0-LFE[a]"`

 ... and who knows what else.

 Currently, a somewhat useful alternative appears to be to explicitly
 convert 5.1(side) to 5.1 (with something like `-channel_layout 5.1`) ...
 but I've only loosely checked the stereo output of that so far and cannot
 yet say where the other channels land.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/7273#comment:8>
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