Captioning (and audio transcripts) rely on clean text transcripts that accurately reflect the content of the audio tracks they accompany. A text transcript can suffice for delivery alongside an audio file, such as a podcast or MP3. A user can read the transcript when the audio is unavailable.
4 ways to obtain a quality transcript
Start each video project with a written script
If you have creative influence over your video project, consider using a written script where possible. A script provides a solid basis for captioning the final product, and could include speaker identification, descriptions of environmental and ambient sounds, and other information to provide context to your captioning consumers. A script can also enforce a level of quality control and predictability during the production, ensuring that speakers impart the message accurately and in line with the intentions of the video producers.
Obtain the transcript or caption from the owner of the video
Video that comes from a studio, a clearing house, or some other commercial distributor may already have trancripts or captions available. Check with your media vendor to see whether your video is transcribed or captioned.
Transcribe your video project post-production
If your video is unscripted, or the script is missing, you can consider transcribing the content yourself. Most of the time, this means listening to the video's audio track, pausing the playback, typing what you've just heard, and repeating this process until all of the audio is contained in a text file. Afterward, you will need to review your new transcript, correcting typos, misspellings, and other errors until you have a clean and accurate rendering of your media's audio track.
Use a transcription or captioning service
This isn't technically DIY, but it's a good option. Transcription and captioning services cost money, but they often produce higher-quality, faster turnaround results than you can do in-house. Services range from about $1/minute of audio for simple transcription to $3 or more per minute of completed captioning. Results are generally guaranteed.