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Posted to dev@tika.apache.org by "dschmidt (via GitHub)" <gi...@apache.org> on 2026/07/14 14:28:40 UTC

[PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

dschmidt opened a new pull request, #2953:
URL: https://github.com/apache/tika/pull/2953

   Part 2 of TIKA-4779, following up on #2947 with the three audio properties that need parser work rather than plain mapping: `audio:bitrate` (average, bits per second), `audio:is-variable-bitrate` and `audio:has-drm`, defined under Tika's own namespace in `Audio.java`.
   
   **MP3:** the parser already walks every audio frame for the duration, and since frame duration does not depend on the bitrate, the plain mean over the frames is the exact average and differing frame bitrates are an exact VBR signal. The one special case is the Xing/Info/VBRI tag frame some encoders write first: it is a valid MPEG frame without audio, often at a different bitrate than the stream, so it is detected and excluded (a CBR file with an Info tag would otherwise be misreported as VBR, there is a fixture proving exactly that). I deliberately did not go the usual route of reading the bitrate from the Xing table itself: the full frame walk already happens for the duration, so the exact mean is free and works for files without any tag frame.
   
   **Vorbis:** the identification header declares upper/nominal/lower rates. Nominal maps to `audio:bitrate`; a zero-width bracket (upper == lower, no nominal) also pins an exact rate. Fixed rate means all three declared rates agree, or only a zero-width bracket is declared; anything else counts as variable.
   
   **MP4/M4A:** a `TikaMp4SoundHandler` (same extension pattern as TIKA-2861) structurally walks the sample description entries. Protected sample entry formats (`drms`, `enca`) set `audio:has-drm`; these markers are readable by design since DRM encrypts the payload, not the metadata. The average bitrate comes from the esds elementary stream descriptor, located as a child box of the entry (honoring the version-dependent entry layout, QuickTime `wave` wrappers and the optional ES descriptor fields). I deliberately avoided scanning the stsd bytes for fourcc markers: codec private data or a URL field can legally contain the string `sinf`, and a fixture covers that false positive.
   
   For files with several audio tracks the properties reflect the last sound track's sample description, consistent with how the existing MP4 audio metadata behaves.
   
   Note: the `hdlr` dispatch hook in `TikaMp4BoxHandler` overlaps with #2936; whichever merges second has a trivial rebase.
   
   Tests run against real files where the repo has them (`testMP4.m4a` with a declared average of 256000, the constant bitrate MP3 fixtures, `testVORBIS.ogg` copied from the integration tests). Synthetic fixtures cover only what no real specimen exercises: a VBR MP3, a CBR MP3 with an Info tag frame, a `drms` protected M4A and an M4A whose ES descriptor uses the optional fields.
   


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Re: [PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

Posted by "tballison (via GitHub)" <gi...@apache.org>.
tballison commented on PR #2953:
URL: https://github.com/apache/tika/pull/2953#issuecomment-5005293499

   Will merge once conflicts are resolved and we have a clean build. Thank you @dschmidt !


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Re: [PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

Posted by "dschmidt (via GitHub)" <gi...@apache.org>.
dschmidt commented on PR #2953:
URL: https://github.com/apache/tika/pull/2953#issuecomment-5038828085

   ooooh, sweeet! πŸ™ƒ


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Re: [PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

Posted by "tballison (via GitHub)" <gi...@apache.org>.
tballison commented on PR #2953:
URL: https://github.com/apache/tika/pull/2953#issuecomment-4980711144

   Small nits from my agent:
   ```
     1. Audio.HAS_DRM javadoc overstates the implementation. It says "…or a protection scheme ('sinf') box," but the
     code only flags the drms/enca sample-entry formats β€” it never independently detects a standalone sinf. In
     practice enca entries always carry sinf, so coverage is fine, but the doc implies a check that isn't there. Trim
     the sinf mention or reword to "protected sample entry formats."
     2. Multi-track asymmetry. BITRATE is last-track-wins (documented), but HAS_DRM is any-track-wins (only ever set
     to true). Defensible β€” arguably more correct for DRM β€” but the two properties describe "the last track" and "any
     track" respectively. Worth a one-line note in the PR/javadoc if you want it explicit.
     3. M4A with avgBitrate=0 gets no BITRATE even when maxBitrate>0 (some encoders only set max). Acceptable given
     the property is defined as average; just a coverage gap, not a bug.
     4. Vorbis nominal-only β‡’ is-variable-bitrate=true is aggressive but correct in practice (nominal-only is
     quality-mode VBR). Fine as-i
   ```
   Not sure you need to address any of them. The add vs set, number 2 is ... not clear what the right answer is?


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Re: [PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

Posted by "dschmidt (via GitHub)" <gi...@apache.org>.
dschmidt commented on PR #2953:
URL: https://github.com/apache/tika/pull/2953#issuecomment-4981499808

   1. was a leftover from an earlier iteration that scanned raw bytes for sinf; the javadoc now names only the protected sample entry formats.
   2. I think the asymmetry is the correct semantics rather than an accident: has-drm answers "does this file contain protected audio anywhere", so any track sets it, while bitrate describes one stream and follows the same last-sound-track convention as the rest of the MP4 audio metadata. Both javadocs now state their multi-track semantics explicitly. 3. is deliberate: the property is defined as the average, and deriving one from maxBitrate would report a number the encoder never claimed; a separate max-bitrate property would be the clean extension if anyone ever needs it.
   4. agreed, leaving as is.


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Re: [PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

Posted by "dschmidt (via GitHub)" <gi...@apache.org>.
dschmidt commented on PR #2953:
URL: https://github.com/apache/tika/pull/2953#issuecomment-5008618651

   I wasnt sure, if you wanted a rebase or a merge for this - so I pushed a merge commit (it's tiny after all).
   
   Feel free to squash obviously :) 


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Re: [PR] TIKA-4779: Add audio:bitrate, audio:is-variable-bitrate and audio:has-drm [tika]

Posted by "tballison (via GitHub)" <gi...@apache.org>.
tballison merged PR #2953:
URL: https://github.com/apache/tika/pull/2953


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