doc: clearer doc

Author: tobbee

README.md

@@ -6,13 +6,16 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/edgeware/mp4ff)](https://goreportcard.com/report/github.com/edgeware/mp4ff)
 [![license](https://img.shields.io/github/license/edgeware/mp4ff.svg)](https://github.com/edgeware/mp4ff/blob/master/LICENSE.md)
 
-MP4/ISOBMFF media file parser and writer. Focused on fragmented files as used for streaming in DASH, MSS and HLS fMP4.
+Package mp4ff implements MP4 media file parser and writer for AVC video, AAC audio and stpp/wvtt subtitles.
+Focused on fragmented files as used for streaming in DASH, MSS and HLS fMP4.
 
 ## Library
 
-The library has functions for parsing (called Decode) and writing (Encode).
+The library has functions for parsing (called Decode) and writing (Encode) in the package `mp4ff/mp4`.
+It also contains codec specific parsing of of AVC/H.264 including complete parsing of
+SPS and PPS in the package `mp4ff.avc`.
 
-Traditional multiplexed non-fragmented mp4 files can be parsed and decoded, see `examples/segment`.
+Traditional multiplexed non-fragmented mp4 files can also be parsed and decoded, see `examples/segment`.
 
 The focus is, however, on non-multiplexed single-track fragmented mp4 files as used in DASH, HLS, and CMAF.
 
@@ -114,7 +117,7 @@ it can be calculated. It is set to `MoofBox.Size()+8`.
 
 Some simple command line tools are available in `cmd`.
 
-1. `mp4ff-pslister` extracts and displays pps and sps for AVC in an mp4 file
+1. `mp4ff-pslister` extracts and displays pps and sps for AVC in an mp4 file.
 
 ## Example code
 
@@ -133,7 +136,7 @@ The APIs should be fairly stable, but minor non-backwards-compatible tweaks may
 
 MIT, see [LICENSE.md](LICENSE.md).
 
-Some code in pkg/mp4, es from or is based on https://github.com/jfbus/mp4 which has
+Some code in pkg/mp4, comes from or is based on https://github.com/jfbus/mp4 which has
 `Copyright (c) 2015 Jean-François Bustarret`.
 
 Some code in pkg/bits comes from or is based on https://github.com/tcnksm/go-casper/tree/master/internal/bits

avc/doc.go

@@ -0,0 +1,4 @@
+/*
+Package avc implements parsing of AVC(H.264) nal headers, slice headers and complete SPS and PPS.
+*/
+package avc

cmd/mp4ff-pslister/main.go

@@ -59,7 +59,7 @@ func main() {
 			avcC := stsd.AvcX.AvcC
 			trackID := trak.Tkhd.TrackID
 			if *verbose {
-				fmt.Printf("Videavo track ID=%d\n", trackID)
+				fmt.Printf("Video track ID=%d\n", trackID)
 			}
 			var spsInfo *avc.SPS
 			var err error

doc.go

@@ -1,5 +1,6 @@
 /*
-Package mp4ff implements MP4 media file parser and writer.
+Package mp4ff implements MP4 media file parser and writer for AVC video, AAC audio and stpp/wvtt subtitles.
+Focused on fragmented files as used for streaming in DASH, MSS and HLS fMP4.
 
 MP4 library
 

examples/resegmenter/main.go

@@ -1,10 +1,10 @@
-// mp4ff-resegmenter resegments mp4 files into concatenated segments with new duration.
+// resegmenter resegments mp4 files into concatenated segments with new duration.
 //
-// The mp4 files must look like a CMAF track with init segment and media segments.
+// The input file must be a CMAF track with init segment and media segments.
 //
 //   Usage:
 //
-//    mp4ff-resegmenter -f <input.mp4> -o <output.mp4> -b <chunk_dur>
+//    resegmenter -f <input.mp4> -o <output.mp4> -b <chunk_dur>
 //    -b int
 //         Required: chunk duration (ticks)
 //    -f string

examples/segmenter/main.go

@@ -1,9 +1,9 @@
 // segmenter segments a progressive mp4 file into audio and video segments
 //
-// There should be at most one audio and one video track in the file.
+// There should be at most one audio and one video track in the input.
 // The output files will be named as
-//   init segments: <output>_a.mp4 and <output>_v.mp4
-//   media segments: <output>_a_<n>.m4s and <output>_v_<n>.m4s where n >= 1
+// init segments: <output>_a.mp4 and <output>_v.mp4
+// media segments: <output>_a_<n>.m4s and <output>_v_<n>.m4s where n >= 1
 //
 //   Usage:
 //

examples/tree/main.go

@@ -1,4 +1,4 @@
-// mp4ff-tree print a tree of the box structure of a file.
+// tree prints a tree of the box structure of a file using the Dump method of boxes.
 //
 //   Usage:
 //
@@ -30,5 +30,11 @@ func main() {
 	}
 	defer ifd.Close()
 	parsedMp4, err := mp4.DecodeFile(ifd)
-	parsedMp4.Dump(os.Stdout, "  ")
+	if err != nil {
+		log.Fatal(err)
+	}
+	err = parsedMp4.Dump(os.Stdout, "  ")
+	if err != nil {
+		log.Fatal(err)
+	}
 }