Does ffmpeg's aac encoder need a audio bitrate?











up vote
2
down vote

favorite












What happens if you do not set a audio bitrate in the aac encoder ?



-ab 128k


Does it automaticly select the highest bitrate it can or something i am curious if i should do this or if it will be bad i see no difference.






ffmpeg aac







share|improve this question






















  • Why would you not try it? And then for the output file do ffmpeg -i outputfile. It will tell you what bitrate the audio is at. No encoder detects incoming bitrate it justs falls to defaults.
    – Rajib
    Jan 1 '15 at 14:25

















up vote
2
down vote

favorite












What happens if you do not set a audio bitrate in the aac encoder ?



-ab 128k


Does it automaticly select the highest bitrate it can or something i am curious if i should do this or if it will be bad i see no difference.






ffmpeg aac







share|improve this question






















  • Why would you not try it? And then for the output file do ffmpeg -i outputfile. It will tell you what bitrate the audio is at. No encoder detects incoming bitrate it justs falls to defaults.
    – Rajib
    Jan 1 '15 at 14:25















up vote
2
down vote

favorite









up vote
2
down vote

favorite











What happens if you do not set a audio bitrate in the aac encoder ?



-ab 128k


Does it automaticly select the highest bitrate it can or something i am curious if i should do this or if it will be bad i see no difference.






ffmpeg aac







share|improve this question













What happens if you do not set a audio bitrate in the aac encoder ?



-ab 128k


Does it automaticly select the highest bitrate it can or something i am curious if i should do this or if it will be bad i see no difference.






ffmpeg aac




ffmpeg aac






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Jan 1 '15 at 11:30









C0nw0nk

184311




184311












  • Why would you not try it? And then for the output file do ffmpeg -i outputfile. It will tell you what bitrate the audio is at. No encoder detects incoming bitrate it justs falls to defaults.
    – Rajib
    Jan 1 '15 at 14:25




















  • Why would you not try it? And then for the output file do ffmpeg -i outputfile. It will tell you what bitrate the audio is at. No encoder detects incoming bitrate it justs falls to defaults.
    – Rajib
    Jan 1 '15 at 14:25


















Why would you not try it? And then for the output file do ffmpeg -i outputfile. It will tell you what bitrate the audio is at. No encoder detects incoming bitrate it justs falls to defaults.
– Rajib
Jan 1 '15 at 14:25






Why would you not try it? And then for the output file do ffmpeg -i outputfile. It will tell you what bitrate the audio is at. No encoder detects incoming bitrate it justs falls to defaults.
– Rajib
Jan 1 '15 at 14:25












2 Answers
2






active

oldest

votes

















up vote
5
down vote



accepted










It totally depends on the AAC encoder you are using. ffmpeg can use several AAC encoders:





  • aac (ffmpeg-internal) – defaults to 128 kBit/s for both mono and stereo.


  • libfdk-aac – defaults to 128 kBit/s for stereo and 96 kBit/s CBR for mono.


In general, you should choose a higher bitrate than the default for aac. This is because it produces somewhat lower quality than libfdk-aac at the same bitrate. Do that by setting -b:a appropriately, e.g. -b:a 192k.



I tried to summarize the VBR options on my homepage, and the FFmpeg Wiki has good info on AAC encoding as well as some example commands.



Also, when you see a line similar to this in ffmpeg's log output:



Stream #0:0: Audio: aac (libfdk_aac) (mp4a / 0x6134706D), … 96 kb/s


Then the kb/s shown here do not necessarily reflect what the encoder will really use, as it's up to the specific implementation.




There are also some encoders that are not supported anymore by ffmpeg:





  • libfaac – defaults to VBR setting of 100, which results in about 128 kBit/s for stereo audio (reference).


  • libvo-aacenc – defaults to 128 kBit/s for both mono and stereo.

  • libaacplus






share|improve this answer























  • Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
    – C0nw0nk
    Jan 1 '15 at 15:49






  • 1




    The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
    – slhck
    Jan 1 '15 at 16:01










  • Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
    – slhck
    Jan 1 '15 at 16:02










  • Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
    – C0nw0nk
    Jan 1 '15 at 16:26


















up vote
-1
down vote













Libfaac sets a default bitrate. 128k for a stereo input and 96k for mono.






share|improve this answer





















  • The OP is talking about "ffmpeg's aac encoder", not FAAC.
    – slhck
    Jan 1 '15 at 15:29










  • True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
    – stib
    Jan 2 '15 at 11:01










  • Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
    – slhck
    Jan 2 '15 at 11:06











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
5
down vote



accepted










It totally depends on the AAC encoder you are using. ffmpeg can use several AAC encoders:





  • aac (ffmpeg-internal) – defaults to 128 kBit/s for both mono and stereo.


  • libfdk-aac – defaults to 128 kBit/s for stereo and 96 kBit/s CBR for mono.


In general, you should choose a higher bitrate than the default for aac. This is because it produces somewhat lower quality than libfdk-aac at the same bitrate. Do that by setting -b:a appropriately, e.g. -b:a 192k.



I tried to summarize the VBR options on my homepage, and the FFmpeg Wiki has good info on AAC encoding as well as some example commands.



Also, when you see a line similar to this in ffmpeg's log output:



Stream #0:0: Audio: aac (libfdk_aac) (mp4a / 0x6134706D), … 96 kb/s


Then the kb/s shown here do not necessarily reflect what the encoder will really use, as it's up to the specific implementation.




There are also some encoders that are not supported anymore by ffmpeg:





  • libfaac – defaults to VBR setting of 100, which results in about 128 kBit/s for stereo audio (reference).


  • libvo-aacenc – defaults to 128 kBit/s for both mono and stereo.

  • libaacplus






share|improve this answer























  • Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
    – C0nw0nk
    Jan 1 '15 at 15:49






  • 1




    The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
    – slhck
    Jan 1 '15 at 16:01










  • Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
    – slhck
    Jan 1 '15 at 16:02










  • Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
    – C0nw0nk
    Jan 1 '15 at 16:26















up vote
5
down vote



accepted










It totally depends on the AAC encoder you are using. ffmpeg can use several AAC encoders:





  • aac (ffmpeg-internal) – defaults to 128 kBit/s for both mono and stereo.


  • libfdk-aac – defaults to 128 kBit/s for stereo and 96 kBit/s CBR for mono.


In general, you should choose a higher bitrate than the default for aac. This is because it produces somewhat lower quality than libfdk-aac at the same bitrate. Do that by setting -b:a appropriately, e.g. -b:a 192k.



I tried to summarize the VBR options on my homepage, and the FFmpeg Wiki has good info on AAC encoding as well as some example commands.



Also, when you see a line similar to this in ffmpeg's log output:



Stream #0:0: Audio: aac (libfdk_aac) (mp4a / 0x6134706D), … 96 kb/s


Then the kb/s shown here do not necessarily reflect what the encoder will really use, as it's up to the specific implementation.




There are also some encoders that are not supported anymore by ffmpeg:





  • libfaac – defaults to VBR setting of 100, which results in about 128 kBit/s for stereo audio (reference).


  • libvo-aacenc – defaults to 128 kBit/s for both mono and stereo.

  • libaacplus






share|improve this answer























  • Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
    – C0nw0nk
    Jan 1 '15 at 15:49






  • 1




    The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
    – slhck
    Jan 1 '15 at 16:01










  • Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
    – slhck
    Jan 1 '15 at 16:02










  • Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
    – C0nw0nk
    Jan 1 '15 at 16:26













up vote
5
down vote



accepted







up vote
5
down vote



accepted






It totally depends on the AAC encoder you are using. ffmpeg can use several AAC encoders:





  • aac (ffmpeg-internal) – defaults to 128 kBit/s for both mono and stereo.


  • libfdk-aac – defaults to 128 kBit/s for stereo and 96 kBit/s CBR for mono.


In general, you should choose a higher bitrate than the default for aac. This is because it produces somewhat lower quality than libfdk-aac at the same bitrate. Do that by setting -b:a appropriately, e.g. -b:a 192k.



I tried to summarize the VBR options on my homepage, and the FFmpeg Wiki has good info on AAC encoding as well as some example commands.



Also, when you see a line similar to this in ffmpeg's log output:



Stream #0:0: Audio: aac (libfdk_aac) (mp4a / 0x6134706D), … 96 kb/s


Then the kb/s shown here do not necessarily reflect what the encoder will really use, as it's up to the specific implementation.




There are also some encoders that are not supported anymore by ffmpeg:





  • libfaac – defaults to VBR setting of 100, which results in about 128 kBit/s for stereo audio (reference).


  • libvo-aacenc – defaults to 128 kBit/s for both mono and stereo.

  • libaacplus






share|improve this answer














It totally depends on the AAC encoder you are using. ffmpeg can use several AAC encoders:





  • aac (ffmpeg-internal) – defaults to 128 kBit/s for both mono and stereo.


  • libfdk-aac – defaults to 128 kBit/s for stereo and 96 kBit/s CBR for mono.


In general, you should choose a higher bitrate than the default for aac. This is because it produces somewhat lower quality than libfdk-aac at the same bitrate. Do that by setting -b:a appropriately, e.g. -b:a 192k.



I tried to summarize the VBR options on my homepage, and the FFmpeg Wiki has good info on AAC encoding as well as some example commands.



Also, when you see a line similar to this in ffmpeg's log output:



Stream #0:0: Audio: aac (libfdk_aac) (mp4a / 0x6134706D), … 96 kb/s


Then the kb/s shown here do not necessarily reflect what the encoder will really use, as it's up to the specific implementation.




There are also some encoders that are not supported anymore by ffmpeg:





  • libfaac – defaults to VBR setting of 100, which results in about 128 kBit/s for stereo audio (reference).


  • libvo-aacenc – defaults to 128 kBit/s for both mono and stereo.

  • libaacplus







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 22 at 9:45

























answered Jan 1 '15 at 15:44









slhck

158k47437461




158k47437461












  • Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
    – C0nw0nk
    Jan 1 '15 at 15:49






  • 1




    The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
    – slhck
    Jan 1 '15 at 16:01










  • Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
    – slhck
    Jan 1 '15 at 16:02










  • Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
    – C0nw0nk
    Jan 1 '15 at 16:26


















  • Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
    – C0nw0nk
    Jan 1 '15 at 15:49






  • 1




    The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
    – slhck
    Jan 1 '15 at 16:01










  • Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
    – slhck
    Jan 1 '15 at 16:02










  • Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
    – C0nw0nk
    Jan 1 '15 at 16:26
















Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
– C0nw0nk
Jan 1 '15 at 15:49




Thanks so what is the recommended bitrate i should use with aac before i had it set to -ab 192k and i kept getting bit_rate width height error what is kind of annoying.
– C0nw0nk
Jan 1 '15 at 15:49




1




1




The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
– slhck
Jan 1 '15 at 16:01




The recommended bitrate depends on what your application is, and what encoder you are using. For web video, you probably want 128 kBit/s but not much more. For listening to music, I'd go higher than that. For the internal AAC encoder, 192 kBit/s is very good quality. I don't know what a "bit_rate width height error" is, though. If that is your real problem, then you should ask a new question about the error and show the complete, uncut command line output from ffmpeg.
– slhck
Jan 1 '15 at 16:01












Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
– slhck
Jan 1 '15 at 16:02




Unless it's this question you already asked: superuser.com/questions/805196/… — you got a good answer there already.
– slhck
Jan 1 '15 at 16:02












Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
– C0nw0nk
Jan 1 '15 at 16:26




Thanks i set it to be -ab 128k and i will just wait and see if that error ever comes back.
– C0nw0nk
Jan 1 '15 at 16:26












up vote
-1
down vote













Libfaac sets a default bitrate. 128k for a stereo input and 96k for mono.






share|improve this answer





















  • The OP is talking about "ffmpeg's aac encoder", not FAAC.
    – slhck
    Jan 1 '15 at 15:29










  • True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
    – stib
    Jan 2 '15 at 11:01










  • Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
    – slhck
    Jan 2 '15 at 11:06















up vote
-1
down vote













Libfaac sets a default bitrate. 128k for a stereo input and 96k for mono.






share|improve this answer





















  • The OP is talking about "ffmpeg's aac encoder", not FAAC.
    – slhck
    Jan 1 '15 at 15:29










  • True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
    – stib
    Jan 2 '15 at 11:01










  • Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
    – slhck
    Jan 2 '15 at 11:06













up vote
-1
down vote










up vote
-1
down vote









Libfaac sets a default bitrate. 128k for a stereo input and 96k for mono.






share|improve this answer












Libfaac sets a default bitrate. 128k for a stereo input and 96k for mono.







share|improve this answer












share|improve this answer



share|improve this answer










answered Jan 1 '15 at 13:53









stib

2,30341930




2,30341930












  • The OP is talking about "ffmpeg's aac encoder", not FAAC.
    – slhck
    Jan 1 '15 at 15:29










  • True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
    – stib
    Jan 2 '15 at 11:01










  • Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
    – slhck
    Jan 2 '15 at 11:06


















  • The OP is talking about "ffmpeg's aac encoder", not FAAC.
    – slhck
    Jan 1 '15 at 15:29










  • True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
    – stib
    Jan 2 '15 at 11:01










  • Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
    – slhck
    Jan 2 '15 at 11:06
















The OP is talking about "ffmpeg's aac encoder", not FAAC.
– slhck
Jan 1 '15 at 15:29




The OP is talking about "ffmpeg's aac encoder", not FAAC.
– slhck
Jan 1 '15 at 15:29












True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
– stib
Jan 2 '15 at 11:01




True. But if I don't specify an encoder libFAAC is the default. Maybe it's just the way my build of ffmpeg works.
– stib
Jan 2 '15 at 11:01












Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
– slhck
Jan 2 '15 at 11:06




Yeah, that's assuming ffmpeg is built with libfaac. In the default configuration, it will fail to convert to AAC, since the internal AAC encoder needs the -strict experimental flag.
– slhck
Jan 2 '15 at 11:06


















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