Mp3Extractor: Support files with (slightly) incorrectly declared ID3 tag lengths

Version

Media3 pre-release (alpha, beta or RC not in this list)

More version details

Any version but tested with 1.2.0

Devices that reproduce the issue

All

Devices that do not reproduce the issue

None

Reproducible in the demo app?

Yes

Reproduction steps

Try to play a file with multiple large ID3 headers.
Like a small ID3 v1 header followed by an ID3 header larger than 32k

The extractor sniff will fail because only the first ID3 header is taken in account and skipped, so the sniff does not reach the proper frames before the end of the second ID3 header.

Second header that should either be skipped or handled for the gapless data / metadata don't know if there should be a priorisation of ID3 v2 tags over v1 when both are present.

Expected result

The media should play

Actual result

The media does not play because the sniff return false due to large second ID3 header.

Media

I can send in private if necessary.

Bug Report

You will email the zip file produced by adb bugreport to android-media-github@google.com after filing this issue.

@Tolriq

Hi @Tolriq,

Can you please send the media via email for me to take a look?

Sent.

Small why not bump. Still an issue. My local hack is just an hack not good enough to upstream.

Subject: [PATCH] If the file start with ID3 increase the max sniff size
---
Index: libraries/extractor/src/main/java/androidx/media3/extractor/mp3/Mp3Extractor.java
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/libraries/extractor/src/main/java/androidx/media3/extractor/mp3/Mp3Extractor.java b/libraries/extractor/src/main/java/androidx/media3/extractor/mp3/Mp3Extractor.java
--- a/libraries/extractor/src/main/java/androidx/media3/extractor/mp3/Mp3Extractor.java	(revision 07c45b3c4180d0da4d92f76ff0ff3a8c69b029ca)
+++ b/libraries/extractor/src/main/java/androidx/media3/extractor/mp3/Mp3Extractor.java	(revision a37d893d9b226e2923b4d478d3aae76e4efe54bf)
@@ -395,6 +395,9 @@
         input.skipFully(peekedId3Bytes);
       }
     }
+    if (peekedId3Bytes > 0) {
+      searchLimitBytes = MAX_SYNC_BYTES;
+    }
     while (true) {
       if (peekEndOfStreamOrHeader(input)) {
         if (validFrameCount > 0) {

ExoPlayer's Id3Peeker does try to read multiple ID3 tags with the while loop in Id3Peeker (in order to handle the case you describe). We try and advance to the start of the next tag with this line:

media/libraries/extractor/src/main/java/androidx/media3/extractor/Id3Peeker.java

Line 78 in ae9a233

input.advancePeekPosition(framesLength);

In the case of the provided file, this advances one byte too few, so this check fails (because we read 0x094944 = <TAB>ID instead of 0x494443 = ID3).

media/libraries/extractor/src/main/java/androidx/media3/extractor/Id3Peeker.java

Lines 63 to 66 in ae9a233

    
           if (scratch.readUnsignedInt24() != Id3Decoder.ID3_TAG) { 
        
             // Not an ID3 tag. 
        
             break; 
        
           }

The first ID3 tag in this file represents its length as 0x00001070, which is a 'synch safe' int where the MSB of each byte is zero (and ignored), so this evaluates to 2160 in decimal. This is the length without the 10 byte ID3 header (but does include padding) [1], so the next ID3 tag should start at byte 2170, but in fact it starts at 2171.

We can add some fuzziness to the search for the next ID3 tag, but this media is not spec-compliant, so marking this as a feature request rather than a bug.

[1] From https://id3.org/d3v2.3.0

The ID3v2 tag size is the size of the complete tag after unsychronisation, including padding, excluding the header but not excluding the extended header (total tag size - 10).

Add some fuzziness to Mp3Extractor's ID3 tag searching

This is fixed by the commit linked above.

Add some fuzziness to Mp3Extractor's ID3 tag searching

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Mp3Extractor: Support files with (slightly) incorrectly declared ID3 tag lengths #811

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Devices that do not reproduce the issue

Reproducible in the demo app?

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Expected result

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	if (scratch.readUnsignedInt24() != Id3Decoder.ID3_TAG) {
	// Not an ID3 tag.
	break;
	}

Mp3Extractor: Support files with (slightly) incorrectly declared ID3 tag lengths #811

Description

Version

More version details

Devices that reproduce the issue

Devices that do not reproduce the issue

Reproducible in the demo app?

Reproduction steps

Expected result

Actual result

Media

Bug Report

Activity

rohitjoins commented on Nov 15, 2023

Tolriq commented on Nov 15, 2023

Tolriq commented on Jul 21, 2025

icbaker commented on Jul 22, 2025

icbaker commented on Jul 29, 2025

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