Hello all,
I am using ffmpeg/ffprobe, both release 6.1, running on Windows 11 Family.
In the following, I name :
-> "initial movie" : the movie to be reencoded ;
-> "final movie" : the movie produced by the reencoding process.
In order to obtain audio informations about any movie, I use the following
command :
ffprobe "any movie" -v error -select_streams a -print_format json -show_format
-show_streams
When I apply this command to an initial movie :
ffprobe "initial movie" -v error -select_streams a -print_format json
-show_format -show_streams
this is the result of the command :
"index": 1,
"codec_name": "truehd",
"sample_rate": "48000",
"channels": 8,
"channel_layout": "7.1",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"language": "eng",
"title": "TrueHD with Dolby Atmos 7.1",
"BPS-eng": "4211333",
"_STATISTICS_TAGS-eng": "BPS DURATION NUMBER_OF_FRAMES
NUMBER_OF_BYTES"
"index": 2,
"codec_name": "ac3",
"sample_rate": "48000",
"channels": 6,
"channel_layout": "5.1(side)",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"bit_rate": "448000",
"language": "eng",
"title": "Dolby Digital 5.1",
"BPS-eng": "448000",
"_STATISTICS_TAGS-eng": "BPS DURATION NUMBER_OF_FRAMES
NUMBER_OF_BYTES"
"index": 3,
"codec_name": "ac3",
"sample_rate": "48000",
"channels": 6,
"channel_layout": "5.1(side)",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"bit_rate": "448000",
"language": "spa",
"title": "Dolby Digital 5.1",
"BPS-eng": "448000",
"_STATISTICS_TAGS-eng": "BPS DURATION NUMBER_OF_FRAMES
NUMBER_OF_BYTES"
"index": 4,
"codec_name": "ac3",
"sample_rate": "48000",
"channels": 6,
"channel_layout": "5.1(side)",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"bit_rate": "448000",
"language": "fre",
"title": "Dolby Digital 5.1",
"BPS-eng": "448000",
"_STATISTICS_TAGS-eng": "BPS DURATION NUMBER_OF_FRAMES
NUMBER_OF_BYTES"
After, in order to reencode the considered initial movie, I executed the
following command :
ffmpeg -i "initial movie" -y -loglevel error -sn ^
-map 0:a:0 -c:a:0 aac -b:a:0 128k -ar:0 48k -metadata:s:a:0 language=eng ^
-map 0:a:3 -c:a:3 aac -b:a:3 112k -ar:3 48k -metadata:s:a:3 language=fre ^
-map 0:v:0 -vcodec libsvtav1 -vf "scale=960:540" -sws_flags
lanczos+accurate_rnd -b:v 1344k -minrate 1344k -maxrate 1360k ^
-bufsize 2688k "final movie"
When the process is finished, I execute the command for audio infos, for the
final movie :
ffprobe "final movie" -v error -select_streams a -print_format json
-show_format -show_streams
this is the result of the command :
"index": 0,
"codec_name": "aac",
"sample_rate": "48000",
"channels": 8,
"channel_layout": "7.1",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"language": "eng",
"title": "TrueHD with Dolby Atmos 7.1",
"_STATISTICS_TAGS-eng": "BPS DURATION NUMBER_OF_FRAMES
NUMBER_OF_BYTES",
"BPS-eng": "4211333",
"index": 1,
"codec_name": "vorbis",
"sample_rate": "48000",
"channels": 6,
"channel_layout": "5.1",
"r_frame_rate": "0/0",
"avg_frame_rate": "0/0",
"language": "fre",
"title": "Dolby Digital 5.1",
"BPS-eng": "448000",
"_STATISTICS_TAGS-eng": "BPS DURATION NUMBER_OF_FRAMES
NUMBER_OF_BYTES",
As you can see, in the final movie, the wished audio codec specified in the
ffmpeg command :
-> has been respected for the english audio track ;
-> but has been ignored for the french audio track ; the program replaced
unilaterally the wished codec, by another codec.
Then the question is : why did ffmpeg make such a replacement ?
What are the audio characteristics of the initial movie, that led ffmpeg to use
a different audio codec than the one specified ?
Thank you in advance for your replies and advices.
Regards,
HA
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