如何通过编程检测音视频文件是否受DRM保护？FFmpeg能否实现？

1. Programming Methods to Detect DRM Protection #

DRM detection mostly boils down to checking for DRM-specific metadata or container elements in the media file, since encrypted content will carry identifiers for the protection system used. Here are practical, actionable approaches:

• Parse Container Structure Directly
  Most DRM systems embed protection info in standard container boxes:

  • For MP4/M4V files: Look for the pssh (Protection System Specific Header) box inside the moov container. Each DRM system has a unique UUID in the pssh box:
    • Widevine: edef8ba9-79d6-4ace-a3c8-27dcd51d21ed
    • PlayReady: 9a04f079-9840-4286-ab92-e65be0885f95
    • FairPlay: 94ce86fb-07ff-4f43-adb8-93d2fa968ca2
      You can use language-specific libraries to parse these boxes (e.g., pywidevine for Python, or low-level binary parsing with struct), or build custom logic to scan the file for these UUIDs.

• Check Streaming Manifest Metadata
  For adaptive streaming formats (MPEG-DASH, HLS), DRM details live in the manifest file:

  • DASH (MPD): Look for <ContentProtection> elements with DRM system UUIDs and license server URLs.
  • HLS: Check for EXT-X-KEY tags with METHOD=AES-128 (basic encryption) or METHOD=SAMPLE-AES (often paired with DRM like FairPlay).

• Leverage Media Parsing Libraries
  Use battle-tested libraries that abstract container parsing:

  • libavformat (FFmpeg's core library): Its API lets you read file metadata and check for encryption flags.
  • GPAC (Multimedia Framework): Tools like mp4box can inspect DRM info programmatically via its API.

2. Can FFmpeg/ffprobe Detect DRM? #

Absolutely! While FFmpeg can't decrypt DRM-protected content without proper license keys, its companion tool ffprobe is ideal for detecting DRM metadata in media files. Here's how to use it:

Command-Line Detection with ffprobe #

• Quick Encryption Check
  Run this command to get a direct yes/no-like indicator of encryption:

  ffprobe -v error -show_entries format_tags=encryption -of default=noprint_wrappers=1:nokey=1 input.mp4
  

  If the output returns encrypted or a DRM system identifier (like com.widevine.alpha), the file has DRM protection.

• Detailed DRM Metadata
  For granular details, dump all stream and format metadata with:

  ffprobe -show_streams -show_format -v quiet input.mp4
  

  Look for key fields like:

  • format_tags:encryption: Top-level encryption status.
  • stream_tags:encryption: Per-stream encryption info (if applicable).
  • For MP4 files, you may also see explicit references to pssh boxes in the output.

Programmatic Detection with FFmpeg's API #

If you're building an application, use libavformat to detect DRM programmatically:

1. Open the media file with avformat_open_input().
2. Check the AVFormatContext's metadata dictionary for keys like encryption.
3. Iterate over each AVStream and inspect their metadata for encryption-related tags.
4. For deeper MP4 inspection, you can dig into the container's internal structures (though this requires familiarity with libavformat internals).

Note: FFmpeg won't decrypt the content, but it will reliably report if DRM protection is present by reading the container's metadata.

内容的提问来源于stack exchange，提问作者RRN