A method for opportunistic source file frame previewing, the method comprising: receiving, from a user, a preview request for a sampling segment of a source file wherein the sampling segment is a continuous set of one or more source frames of the source file wherein the one or more source frames of the source file are encoded; identifying a transcode segment of the source file that comprises the source frames to transcode for the sampling segment; identifying a first source frame in the source file to transcode wherein the first source frame is in the transcode segment of the source file; transcoding the first source frame to generate an initial transcoded frame wherein the initial transcoded frame is the first transcoded frame generated from the source file and wherein the initial transcoded frame is in a format recognizable to a user; storing the initial transcoded frame; identifying one or more other source frames in the source file to transcode wherein the one or more other source frames are in the transcode segment of the source file; transcoding the one or more other source frames to generate one or more additional transcoded frames wherein each of the one or more source frames are transcoded prior to any source frames that are not in the transcode segment being transcoded and wherein each of the one or more additional resultant transcoded frames are in a format recognizable to a user; storing the one or more additional transcoded frames; using one or more transcoded frames to generate a preview segment wherein the preview segment is representative of the sampling segment; and outputting the preview segment, the method further comprising:transcoding a sufficient number of source frames in the transcode segment prior to transcoding any source frames that are not in the transcode segment wherein a sufficient number of source frames in the transcode segment is a set of source frames in the transcode segment that when transcoded and thereafter included in the preview segment comprise a preview segment that will be recognizable to a user as the sampling segment; and transcoding source frames that are not in a transcode segment for a sampling segment of a preview request when there are no source frames to transcode pursuant to any preview request. receiving, from a user, a preview request for a sampling segment of a source file wherein the sampling segment is a continuous set of one or more source frames of the source file wherein the one or more source frames of the source file are encoded; identifying a transcode segment of the source file that comprises the source frames to transcode for the sampling segment; identifying a first source frame in the source file to transcode wherein the first source frame is in the transcode segment of the source file; transcoding the first source frame to generate an initial transcoded frame wherein the initial transcoded frame is the first transcoded frame generated from the source file and wherein the initial transcoded frame is in a format recognizable to a user; storing the initial transcoded frame; identifying one or more other source frames in the source file to transcode wherein the one or more other source frames are in the transcode segment of the source file; transcoding the one or more other source frames to generate one or more additional transcoded frames wherein each of the one or more source frames are transcoded prior to any source frames that are not in the transcode segment being transcoded and wherein each of the one or more additional resultant transcoded frames are in a format recognizable to a user; storing the one or more additional transcoded frames; using one or more transcoded frames to generate a preview segment wherein the preview segment is representative of the sampling segment; and outputting the preview segment, the method further comprising:transcoding a sufficient number of source frames in the transcode segment prior to transcoding any source frames that are not in the transcode segment wherein a sufficient number of source frames in the transcode segment is a set of source frames in the transcode segment that when transcoded and thereafter included in the preview segment comprise a preview segment that will be recognizable to a user as the sampling segment; and transcoding source frames that are not in a transcode segment for a sampling segment of a preview request when there are no source frames to transcode pursuant to any preview request.