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Codem-transcode

Description

Codem-transcode is an offline video transcoder written in node.js. It

  1. Uses ffmpeg for transcoding
  2. Has a simple HTTP API
  3. Is mostly asynchronous

Codem-transcode can be used in conjunction with Codem-schedule (http://github.com/NPO/codem-schedule) for robust job scheduling and notifications or it can be used stand-alone, with or without a custom scheduler.

Requirements

Installation

Installation can be as simple as checking out the code and starting it using:

# node transcoder.js

Configuration

Configuration is done by specifying a CLI option and pointing to a file containing a valid JSON object (http://www.json.org/). Note that node.js' JSON parser is fairly strict so make sure you get the syntax right. An example config is:

{
    "port":        8080,
    "access_log":  "/var/log/access_log",
    "database":    "/var/transcode/jobs.db",
    "slots":       8,
    "interface":   "127.0.0.1",
    "encoder":     "ffmpeg",
    "scratch_dir": "/tmp"
}

Configuration options:

  • port; port to start server on, default 8080
  • interface; which network interface to listen on, default 127.0.0.1 (only localhost)
  • access_log; location to store HTTP access log, default PATH_TO_TRANSCODER/access_log
  • database; location to store sqlite jobs DB, default PATH_TO_TRANSCODER/jobs.db
  • slots; number of transcoding slots to use (i.e. the maximum number of ffmpeg child processes), defaults to the number of CPUs/cores in your machine
  • encoder; path to the ffmpeg binary, if it is in your path specifying only ffmpeg is sufficient, defaults to ffmpeg
  • scratch_dir; temporary files are written here and moved into the destination directory after transcoding, defaults to /tmp

Note that the default config will put the access_log and job database in the same directory as the source. If you wish to put these in a different location please supply your own config.

Usage

After starting the server you can control it using most HTTP CLI tools, such as curl or wget. The HTTP API is as follows:


Request: POST /jobs

Parameters (HTTP POST data, should be valid JSON object):

{
    "source_file": "/PATH/TO/INPUT/FILE.wmv",
    "destination_file":"/PATH/TO/OUTPUT/FILE.mp4",
    "encoder_options": "-acodec libfaac -ab 96k -ar 44100 -vcodec libx264 -vb 416k -vpre slow -vpre baseline -s 320x180 -y -threads 0",
    "callback_urls": ["http://example.com/notifications"]
}

Responses:

  • 202 Accepted - Job accepted
  • 400 Bad Request - Invalid request (format)
  • 503 Service Unavailable - Transcoder not accepting jobs at the moment (all encoding slots are in use)

The callback_urls array is optional and is a list (array) of HTTP endpoints that should be notified once encoding finishes (due to the job being complete or some error condition). All other options are required (source_file, destination_file and encoder_options). Input and output files should be absolute paths.


Request: GET /jobs

Responses:

  • 200 OK - Returns status of all active jobs

Request: GET /jobs/$JOB_ID

Responses:

  • 200 OK - Returns status of job
  • 404 Not Found - Job not found

Examples

Create a new job, transcode "video.wmv" to "video.mp4" using the specified ffmpeg options (96kbit/s audio, 416kbit/s video, 320x180, use as much threads as possible). Requires libx264 support in your ffmpeg.

# curl -d '{"source_file": "/tmp/video.wmv","destination_file":"/tmp/video.mp4","encoder_options": "-acodec libfaac -ab 96k -ar 44100 -vcodec libx264 -vb 416k -vpre slow -vpre baseline -s 320x180 -y -threads 0"}' http://localhost:8080/jobs

Output: {"message":"The transcoder accepted your job.","job_id":"d4b1dfebe6860839b2c21b70f35938d870011682"}

Create a new job, transcode "video.mpg" to "video.webm" using the specified ffmpeg options (total bitrate 512kbit/s, 320x180, use as much threads as possible). Requires libvpx support in your ffmpeg.

# curl -d '{"source_file": "/tmp/video.mpg","destination_file":"/tmp/video.webm","encoder_options": "-vcodec libvpx -b 512000 -s 320x180 -acodec libvorbis -y -threads 0"}' http://localhost:8080/jobs

Output: {"message":"The transcoder accepted your job.","job_id":"c26769be0955339db8f98580c212b7611cacf4dd"}

Get status of all available encoder slots.

# curl http://localhost:8080/jobs

Output: {"max_slots":8,"free_slots":8,"jobs":[]}

or

Output: {"max_slots":8, "free_slots":7, "jobs":[{"id":"da56da6012bda2ce775fa028f056873bcb29cb3b", "status":"processing", "progress":0.12480252764612954, "duration":633, "filesize":39191346, "message":null}]}

Get full status of one job with id "da56da6012bda2ce775fa028f056873bcb29cb3b".

# curl http://localhost:8080/jobs/da56da6012bda2ce775fa028f056873bcb29cb3b

Output: {"id":"da56da6012bda2ce775fa028f056873bcb29cb3b", "status":"processing", "progress":0.21800947867298578, "duration":633, "filesize":39191346, "opts":"{\"source_file\":\"/shared/videos/asf/video.asf\", \"destination_file\":\"/shared/videos/mp4/journaal.mp4\", \"encoder_options\":\"-acodec libfaac -ab 96k -ar 44100 -vcodec libx264 -vb 416k -vpre slow -vpre baseline -s 320x180 -y -threads 0\"}", "message":null, "created_at":1304338160, "updated_at":1304338173}

Tests

All tests are written using jasmine (via jasmine-node). Running them is as easy as:

# jasmine-node test

More specs coming soon.

License

Codem-transcode is released under the MIT license, see LICENSE.txt.

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