ffmpeg-.m4a输出的默认格式是什么? [英] ffmpeg - what is the default format for .m4a output?
问题描述
我有两个命令,其中一个命令将输出格式指定为 -f mp4
:
I have two commands, one in which I specify the output format as -f mp4
:
ffmpeg -i input.wav -ac 1 -c:a libfdk_aac -profile:a aac_he -vbr 2 -f mp4 test_export_1.m4a
让ffmpeg根据扩展名进行猜测的一个:
And one which lets ffmpeg guess based on the extension:
ffmpeg -i input.wav -ac 1 -c:a libfdk_aac -profile:a aac_he -vbr 2 test_export_2.m4a
这给了我两个不同的结果.
This gives me two different results.
第一个:
$ffprobe test_export_1.m4a
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_export_1.m4a':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2mp41
encoder : Lavf58.29.100
Duration: 00:00:07.13, start: 0.000000, bitrate: 40 kb/s
Stream #0:0(und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 39 kb/s (default)
Metadata:
handler_name : SoundHandler
第二个:
$ffprobe test_export_2.m4a
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test_export_2.m4a':
Metadata:
major_brand : M4A
minor_version : 512
compatible_brands: isomiso2
encoder : Lavf58.29.100
Duration: 00:00:07.13, start: 0.000000, bitrate: 40 kb/s
Stream #0:0(und): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 39 kb/s (default)
Metadata:
handler_name : SoundHandler
第一个带有 isom
品牌的游戏无法在Android设备上播放.第二个工作正常.为什么这些输出不同,我如何指定正确的格式来像第二个一样获得 major_brand:M4A
?我正在使用 pydub
来运行命令,这需要格式标志.
The first one with the brand isom
won't play on Android devices. The second one works fine. Why are these outputs different, and how can I specify the correct format to get major_brand : M4A
like the second one? I'm using pydub
to run the commands, which requires a format flag.
推荐答案
.m4a
不是推荐的ISO扩展名,但通常由Apple使用.与 .mp4
相比,它的可接受编解码器列表有限.格式标记为 -f ipod
.
.m4a
is not a recommended ISO extension but is typically used by Apple. It has a limited list of acceptable codecs as compared to .mp4
. Format flag is -f ipod
.
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