Allow thumbnail-only jobs. Extra platform check for path separator / nul file.

Author: Sjoerd Tieleman

README.markdown

@@ -157,10 +157,14 @@ The `thumbnail_options` object is optional and contains a set of thumbnails that
 * A size can be specified in pixels (width x height). If omitted it will generate thumbnails the size of the source video. (optional)
 * A format for the thumbnails. The format must be supported by your ffmpeg binary. If omitted it will generate thumbnails in the JPEG format. Most people will use either "jpg" or "png". (optional)
 
-If you specify thumbnails but somehow they can't be generated, your job will be marked as failed.
+If you specify thumbnails but an error occurs during generation, your job will be marked as failed. If you don't specify a valid `seconds` or `percentages` option thumbnail generation will be skipped but the job can still be completed successfully.
 
 All other options are required (`source_file`, `destination_file` and `encoder_options`). Input and output files must be *absolute* paths.
 
+### Thumbnail-only job
+
+It's possible to only generate thumbnails from a video and not do any transcoding at all. This might come in handy if you're transcoding to lots of different formats and want to keep thumbnail generation separate from transcoding. You achieve this by POSTing a job with `"encoder_options": ""` (empty string) and of course specifying your `thumbnail_options`. In this case `destination_file` should be a _prefix_ for the output file, e.g. `"destination_file": "/Users/codem/output/my_video"` results in thumbnails in `/Users/codem/output/` with filenames such as `my_video-$offset.$format` (where `$offset` is the thumbnail offset in the video and `$format` of course the thumbnail format). All other options remain the same. See the examples.
+
 * * *
 Request: `GET /jobs`
 
@@ -249,6 +253,12 @@ Probe a file using `ffprobe`.
 
     Output: {"ffprobe":{"streams":[ ... stream info ... ],"format":{ ... format info ... }}}}
 
+Thumbnail-only job (160x90 in PNG format every 10% of the video).
+
+    # curl -d '{"source_file": "/tmp/video.mp4","destination_file":"/tmp/thumbnails/video","encoder_options": "", "thumbnail_options": { "percentages": 0.1, "size": "160x90", "format": "png"} }' http://localhost:8080/jobs
+
+    Output: {"message":"The transcoder accepted your job.","job_id":"d4b1dfebe6860839b2c21b70f35938d870011682"}
+    
 ## Issues and support
 
 If you run into any issues while using codem-transcode please use the Github issue tracker to see if it is a known problem

lib/job.js

@@ -8,7 +8,8 @@ var util          = require('util'),
     notifyHandler = require('./notify-handler'),
     logger        = require('./logger'),
     Sequelize     = require('sequelize'),
-    async         = require('async')
+    async         = require('async'),
+    os            = require('os');
 
 var StatusCodes = {
   SUCCESS: "success",
@@ -233,25 +234,35 @@ var Job = JobUtils.getDatabase().define('Job', {
     spawn: function() {
       var job = this;
       if (this.hasInput && this.hasOutputDir && !this.the_process) {
-        var args = this.parsedOpts()['encoder_options'].replace(/\s+/g, " ").split(' ');
-        args.unshift('-i', this.parsedOpts()['source_file']);
+        var args = [];
+        args.push('-i', this.parsedOpts()['source_file']);
 
         var extension = path.extname(this.parsedOpts()['destination_file']);
         var outputDir = path.dirname(this.parsedOpts()['destination_file']);
 
-        var tmpFile = outputDir + "/" + this.internalId + extension;
+        if (this.parsedOpts()['encoder_options'].length > 0) {
+          // "proper" transcoding job
+          args = args.concat(this.parsedOpts()['encoder_options'].replace(/\s+/g, " ").split(' '));
+          var tmpFile = outputDir + path.sep + this.internalId + extension;
 
-        if (config['use_scratch_dir'] == true) {
-          tmpFile = config['scratch_dir'] + "/" + this.internalId + extension;
-        }
+          if (config['use_scratch_dir'] == true) {
+            tmpFile = config['scratch_dir'] + path.sep + this.internalId + extension;
+          }
 
-        args.push(tmpFile);
+          args.push(tmpFile);
 
+          job.tmpFile = tmpFile;
+        } else {
+          // thumbnail only job, but still need to find duration, so we start a "null" job
+          var null_file = (!!os.platform().match(/^win/) ? 'nul' : '/dev/null');
+          args.push('-f', 'null', '-acodec', 'copy', '-vcodec', 'copy', '-y', null_file);
+        }
+        
         var the_process = child_process.spawn(config['encoder'], args);
         the_process.stderr.on('data', function(data) { job.progressHandler(data) });
-        the_process.on('exit', function(code) { job.didFinish(code, tmpFile); });
+        the_process.on('exit', function(code) { job.didFinish(code); });
 
-        this.the_process = the_process;    
+        this.the_process = the_process;
       }
     },
     cancel: function() {
@@ -260,14 +271,14 @@ var Job = JobUtils.getDatabase().define('Job', {
         this.exitHandler(-1, 'job was cancelled');
       }
     },
-    didFinish: function(code, tmpFile) {
+    didFinish: function(code) {
       if (code == 0 && this.parsedOpts()['thumbnail_options']) {
-        this.processThumbnails(tmpFile);
+        this.processThumbnails();
       } else {
-        this.finalize(code, tmpFile);
+        this.finalize(code);
       }
     },
-    processThumbnails: function(tmpFile) {
+    processThumbnails: function() {
       logger.log("Processing thumbnails for job " + this.internalId + ".");
       var thumbOpts = this.parsedOpts()['thumbnail_options'];
       var range = JobUtils.generateRangeFromThumbOpts(thumbOpts, this.duration);
@@ -279,23 +290,23 @@ var Job = JobUtils.getDatabase().define('Job', {
           function(err, results) {
             if (err) {
               job.lastMessage = err.message;
-              job.finalize(1, tmpFile);
+              job.finalize(1);
             } else {
-              job.finalize(0, tmpFile, results);
+              job.finalize(0, results);
             }
           }
         );
       } else {
         // no valid range
         logger.log("No valid thumbnails to process for job " + this.internalId + ". Skipping...");
-        this.finalize(0, tmpFile);
+        this.finalize(0);
       }
     },
     execThumbJob: function(offset) {
       var job = this;
       return function(callback) {
         var thumbOpts = job.parsedOpts()['thumbnail_options'];
-        var args = ['-ss', offset, '-i', job.parsedOpts()['source_file'], '-vframes', '1'];
+        var args = ['-ss', offset, '-i', job.parsedOpts()['source_file'], '-vframes', '1', '-y'];
 
         // Explicit size provided
         if (thumbOpts['size'] && thumbOpts['size'] != 'src') {
@@ -318,35 +329,40 @@ var Job = JobUtils.getDatabase().define('Job', {
         });
       }
     },
-    finalize: function(code, tmpFile, thumbnails) {
+    finalize: function(code, thumbnails) {
       var job = this;
       if (thumbnails) job.thumbnails = JSON.stringify(thumbnails);
 
       if (code == 0) {
-        fs.rename(tmpFile, job.parsedOpts()['destination_file'], function (err) {
-          if (err) {
-            if ( (err.message).match(/EXDEV/) ) {
-              /*
-                EXDEV fix, since util.pump is deprecated, using stream.pipe
-                example from http://stackoverflow.com/questions/11293857/fastest-way-to-copy-file-in-node-js
-              */
-              try {
-                logger.log('ffmpeg finished successfully, trying to copy across partitions');
-                fs.createReadStream(tmpFile).pipe(fs.createWriteStream(job.parsedOpts()['destination_file']));
-                job.exitHandler(code, 'ffmpeg finished succesfully.');
-              } catch (err) {
+        if (job.tmpFile) {
+          fs.rename(job.tmpFile, job.parsedOpts()['destination_file'], function (err) {
+            if (err) {
+              if ( (err.message).match(/EXDEV/) ) {
+                /*
+                  EXDEV fix, since util.pump is deprecated, using stream.pipe
+                  example from http://stackoverflow.com/questions/11293857/fastest-way-to-copy-file-in-node-js
+                */
+                try {
+                  logger.log('ffmpeg finished successfully, trying to copy across partitions');
+                  fs.createReadStream(job.tmpFile).pipe(fs.createWriteStream(job.parsedOpts()['destination_file']));
+                  job.exitHandler(code, 'ffmpeg finished succesfully.');
+                } catch (err) {
+                  logger.log(err);
+                  job.exitHandler(-1, 'ffmpeg finished succesfully, but unable to move file to different partition (' + job.parsedOpts()['destination_file'] + ').');
+                }
+
+              } else {
                 logger.log(err);
-                job.exitHandler(-1, 'ffmpeg finished succesfully, but unable to move file to different partition (' + job.parsedOpts()['destination_file'] + ').');
+                job.exitHandler(-1, 'ffmpeg finished succesfully, but unable to move file to destination (' + job.parsedOpts()['destination_file'] + ').');
               }
-
             } else {
-              logger.log(err);
-              job.exitHandler(-1, 'ffmpeg finished succesfully, but unable to move file to destination (' + job.parsedOpts()['destination_file'] + ').');
+              job.exitHandler(code, 'ffmpeg finished succesfully.');
             }
-          } else {
-            job.exitHandler(code, 'ffmpeg finished succesfully.');
-          }
-        });
+          });          
+        } else {
+          // No tmpFile, hence no transcoding, only thumbnails
+          job.exitHandler(code, 'finished thumbnail job.');
+        }
       } else {
         job.exitHandler(code, "ffmpeg finished with an error: '" + job.lastMessage + "' (" + code + ").")
       }