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Metadata not always showing AAC bitrate

Posted: Thu Nov 28, 2019 4:46 am
by Tony_T
Description of problem or question:

Metadata not always showing AAC bitrates (occurred on many of my rips)

For example, I selected 3 audio tracks:: 0: English AC3, 2 Chan (192) -> AAC 192 , 0: English AC3, 2 Chan (192) -> AC3 Passthrough and 1: English (commentary track) AC3 (192) -> AAC 192

The Metadata shows no bitrate in the PLEX info, and in the VLC info.
This occurs in many, but not all of my rips.

Here's what PLEX shows that's in the Metadata (note, bitrate of 192 shown in Codec AC3, but nothing in either of the 2 Codec AAC

Codec AAC
Channels 2
Language English
Profile lc
Sampling Rate 48000 Hz
Stream Identifier 2
Display Title English (AAC Stereo)

Codec AC3
Channels 2
Bitrate 192 kbps
Language English
Audio Channel Layout stereo
Sampling Rate 48000 Hz
Stream Identifier 3
Display Title English (AC3 Stereo)

Codec AAC
Channels 2
Language English
Profile lc
Sampling Rate 48000 Hz
Stream Identifier 4
Display Title English (AAC Stereo)


Steps to reproduce the problem (If Applicable):

Select AAC (CoreAudio) Stereo Mixdown, Auto sample rate, 192 bitrate


HandBrake version (e.g., 1.0.0):

1.3.0


Operating system and version (e.g., Ubuntu 16.04 LTS, macOS 10.13 High Sierra, Windows 10 Creators Update):

macOS 10.11.6 (El Capitain)


HandBrake Activity Log ***required*** (see How-to get an activity log)

https://pastebin.com/XXRJ9U9U

Re: Metadata not always showing AAC bitrate

Posted: Thu Nov 28, 2019 2:12 pm
by musicvid
Does MediaInfo show the bitrate?
Missing tags are very common, and don't affect playback. They are merely information for humans.

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 1:57 am
by mduell
That's not a bug.

Feature requests go on github. Even better a pull request for a patch.

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 3:41 am
by Tony_T
musicvid wrote:
Thu Nov 28, 2019 2:12 pm
Does MediaInfo show the bitrate?
Missing tags are very common, and don't affect playback. They are merely information for humans.
Just checked with ffprobe (had this installed with ffmpeg) and it does show the bitrate:
Stream #0:1(eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 197 kb/s

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 3:34 pm
by musicvid
My guess is that is a calculated, rather than a tagged number.
Once again, what does MediaInfo say?
Please be reminded that Handbrake does not write its own codecs, so they have no control over what gets written to metadata tags.

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 4:05 pm
by BradleyS
Indeed, we had another report of this recently. I believe the bit rate is not stored in the container, so some softwares will attempt to glean the information from the stream itself. Inconvenient but not a bug in HandBrake; more of a shortcoming of MediaInfo.

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 5:34 pm
by musicvid
Bitrate Viewer is a fun toy, that has been around forever.

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 11:58 pm
by Tony_T
musicvid wrote:
Fri Nov 29, 2019 3:34 pm
My guess is that is a calculated, rather than a tagged number.
Once again, what does MediaInfo say?
Please be reminded that Handbrake does not write its own codecs, so they have no control over what gets written to metadata tags.
ffprobe (posted above) gives the same (if not more) info as MediaInfo.
Bitrate encoded as 197 (I selected 192 in HB)
Looks like a bug when HB creates the metadata

Re: Metadata not always showing AAC bitrate

Posted: Fri Nov 29, 2019 11:59 pm
by Rodeo
HandBrake simply does not write any track statistics tag (metadata about e.g. bitrate etc.), it's not a bug.

Re: Metadata not always showing AAC bitrate

Posted: Sat Nov 30, 2019 12:08 am
by Tony_T
Rodeo wrote:
Fri Nov 29, 2019 11:59 pm
HandBrake simply does not write any track statistics tag (metadata about e.g. bitrate etc.), it's not a bug.
I understand now. The bitrate is encoded as I selected, so all is good.

Re: Metadata not always showing AAC bitrate

Posted: Sat Nov 30, 2019 12:09 am
by BradleyS
ffprobe actually samples some of the audio stream to determine the bit rate. HandBrake's AAC encoders are not constant bit rate, they're variable/average, so it will fluctuate above and below 192 throughout the stream depending on the complexity of the source audio.

Re: Metadata not always showing AAC bitrate

Posted: Sat Nov 30, 2019 7:17 am
by musicvid
I only wanted to compare the outputs to MediaInfo, which uses different fallback methods to calculate a number of parameters. Glad you found a solution.