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How to Check an MP4 Export for Codecs, Audio, and Subtitles

Use a sample MP4 to check its video codec, dimensions, frame rate, audio tracks, and subtitles. Then run the same checks on your own export.

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Open the exported MP4 and compare its video, audio, and subtitle tracks with what you meant to deliver. Start with the track counts: if you expected two audio languages and the file contains only one audio track, the second one did not make it into the export as a separate track.

MP4 is the container that holds the tracks. H.264 is one codec that can encode the video inside it. The .mp4 extension alone does not tell you which codecs or tracks the file contains.

What to check before you deliver

  1. Video tracks: Compare the Codec, Dimensions, and Frame rate with your delivery requirements.
  2. Audio tracks: Count the tracks, then look at the Language, Codec, and Channels for each one. A language tag is a label; listen to each track to make sure it contains the intended audio.
  3. Subtitle tracks: Check the count and language of any selectable subtitle tracks. Subtitles burned into the picture are part of the video and will not appear in this list. If you delivered subtitles as a separate file, check that file alongside the MP4.

Inspect an MP4 Download the sample MP4

Try it with a sample MP4

In Video Information, select Choose file and open the downloaded sample. Under File details, the duration is 2 seconds. The video section opens by default; expand Audio tracks and Subtitle tracks to see the rest of the results:

  • Video tracks (1): H.264 / AVC, 160 × 90 pixels, 24 fps.
  • Audio tracks (2): AAC-LC, mono, 48,000 Hz each. The tracks are tagged en and zh and contain test tones.
  • Subtitle tracks (1): Timed Text, tagged en.

Other ways to check an MP4 locally

Use the same sample MP4 to compare a command-line report, a desktop track list, and actual playback.

List every track with ffprobe

With ffprobe installed, run this in the folder where you saved the sample. For your own export, replace sample.mp4 with its file name or path.

ffprobe -v error -show_streams -of json "sample.mp4"

The JSON streams array should contain four entries:

  • Index 0, video: h264, 160 × 90, with avg_frame_rate of 24/1 (24 fps).
  • Indexes 1 and 2, audio: aac with profile LC, one channel and 48,000 Hz each. Under tags.language, expect eng and zho, respectively.
  • Index 3, subtitle: mov_text (Timed Text), tagged eng.

Inspect the tracks in MediaInfo

  1. Open the sample in the MediaInfo desktop app and switch to the Tree view.
  2. Check Video for AVC (H.264), 160 × 90, and 24 fps. Under the two Audio entries, compare the format, channels, sample rate, and language.
  3. Check Text for one English subtitle track. Language labels describe the file's metadata; they do not verify the spoken audio or subtitle text.

Listen to the audio and check subtitles in VLC

  1. Open the sample in VLC. Use Audio → Audio Track to select each track and replay the clip. The English-tagged track plays a lower tone and the Chinese-tagged track plays a higher tone; neither contains speech.
  2. Open Subtitle → Sub Track on Windows or Linux, or Subtitles → Subtitles Track on macOS. Select the embedded English track and replay from the start. Look for “Synthetic subtitle” from about 0.25 to 1.75 seconds.
  3. Disable the subtitle track and replay once more. The text should disappear. For your own export, check each track's actual content and timing in the player or device that will be used for delivery.

What to do if the results differ

If your export is missing a track, check the audio or subtitle selections in your exporter, then inspect the new file after exporting again. If a track exists but its language is missing or wrong, check the label in your export settings and verify the actual track in the player you plan to use.

A listed subtitle track confirms that it exists. Enable it in your target player to check the text and timing. The metadata can still be available if the browser cannot preview the file; use the track list to check the export and try playback separately.