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isomp4: Refactor various state variables into a mux_mode var

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Instead of checking various state variables around the muxer,
track the current muxing mode in a single 'mux_mode' enum.

Add some implementation notes about the different mux modes
This commit is contained in:
Jan Schmidt 2015-04-01 11:15:38 +11:00
parent 67a11a5acf
commit fe739b7f88
2 changed files with 269 additions and 144 deletions
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314
gst/isomp4/gstqtmux.c
View file

@ -127,6 +127,58 @@
GST_DEBUG_CATEGORY_STATIC (gst_qt_mux_debug);
#define GST_CAT_DEFAULT gst_qt_mux_debug
/* Hacker notes.
*
* The basic building blocks of MP4 files are:
* - an 'ftyp' box at the very start
* - an 'mdat' box which contains the raw audio/video/subtitle data;
* this is just a bunch of bytes, completely unframed and possibly
* unordered with no additional meta-information
* - a 'moov' box that contains information about the different streams
* and what they contain, as well as sample tables for each stream
* that tell the demuxer where in the mdat box each buffer/sample is
* and what its duration/timestamp etc. is, and whether it's a
* keyframe etc.
* Additionally, fragmented MP4 works by writing chunks of data in
* pairs of 'moof' and 'mdat' boxes:
* - 'moof' boxes, header preceding each mdat fragment describing the
* contents, like a moov but only for that fragment.
* - a 'mfra' box for Fragmented MP4, which is written at the end and
* contains a summary of all fragments and seek tables.
*
* Currently mp4mux can work in 3 different modes / generate 3 types
* of output files/streams:
*
* - Normal mp4: mp4mux will write a little ftyp identifier at the
* beginning, then start an mdat box into which it will write all the
* sample data. At EOS it will then write the moov header with track
* headers and sample tables at the end of the file, and rewrite the
* start of the file to fix up the mdat box size at the beginning.
* It has to wait for EOS to write the moov (which includes the
* sample tables) because it doesn't know how much space those
* tables will be. The output downstream must be seekable to rewrite
* the mdat box at EOS.
*
* - Fragmented mp4: moov header with track headers at start
* but no sample table), followed by N fragments, each containing
* track headers with sample tables followed by some data. Downstream
* does not need to be seekable if the 'streamable' flag is TRUE,
* as the final mfra and total duration will be omitted.
*
* - Fast-start mp4: the goal here is to create a file where the moov
* headers are at the beginning; what mp4mux will do is write all
* sample data into a temp file and build moov header plus sample
* tables in memory and then when EOS comes, it will push out the
* moov header plus sample tables at the beginning, followed by the
* mdat sample data at the end which is read in from the temp file
* Files created in this mode are better for streaming over the
* network, since the client doesn't have to seek to the end of the
* file to get the headers, but it requires copying all sample data
* out of the temp file at EOS, which can be expensive. Downstream does
* not need to be seekable, because of the use of the temp file.
*
*/
#ifndef GST_REMOVE_DEPRECATED
enum
{
@ -1710,10 +1762,60 @@ gst_qt_mux_downstream_is_seekable (GstQTMux * qtmux)
return seekable;
}
static void
gst_qt_mux_prepare_moov_recovery (GstQTMux * qtmux)
{
GSList *walk;
gboolean fail = FALSE;
AtomFTYP *ftyp = NULL;
GstBuffer *prefix = NULL;
GST_DEBUG_OBJECT (qtmux, "Openning moov recovery file: %s",
qtmux->moov_recov_file_path);
qtmux->moov_recov_file = g_fopen (qtmux->moov_recov_file_path, "wb+");
if (qtmux->moov_recov_file == NULL) {
GST_WARNING_OBJECT (qtmux, "Failed to open moov recovery file in %s",
qtmux->moov_recov_file_path);
return;
}
gst_qt_mux_prepare_ftyp (qtmux, &ftyp, &prefix);
if (!atoms_recov_write_headers (qtmux->moov_recov_file, ftyp, prefix,
qtmux->moov, qtmux->timescale, g_slist_length (qtmux->sinkpads))) {
GST_WARNING_OBJECT (qtmux, "Failed to write moov recovery file " "headers");
goto fail;
}
atom_ftyp_free (ftyp);
if (prefix)
gst_buffer_unref (prefix);
for (walk = qtmux->sinkpads; walk && !fail; walk = g_slist_next (walk)) {
GstCollectData *cdata = (GstCollectData *) walk->data;
GstQTPad *qpad = (GstQTPad *) cdata;
/* write info for each stream */
fail = atoms_recov_write_trak_info (qtmux->moov_recov_file, qpad->trak);
if (fail) {
GST_WARNING_OBJECT (qtmux, "Failed to write trak info to recovery "
"file");
break;
}
}
fail:
/* cleanup */
fclose (qtmux->moov_recov_file);
qtmux->moov_recov_file = NULL;
GST_WARNING_OBJECT (qtmux, "An error was detected while writing to "
"recover file, moov recovery won't work");
}
static GstFlowReturn
gst_qt_mux_start_file (GstQTMux * qtmux)
{
GstQTMuxClass *qtmux_klass = (GstQTMuxClass *) (G_OBJECT_GET_CLASS (qtmux));
GstFlowReturn ret = GST_FLOW_OK;
GstCaps *caps;
GstSegment segment;
@ -1732,24 +1834,49 @@ gst_qt_mux_start_file (GstQTMux * qtmux)
gst_pad_set_caps (qtmux->srcpad, caps);
gst_caps_unref (caps);
/* if not streaming or doing fast-start, check if downstream is seekable */
if (!qtmux->streamable) {
/* Default is 'normal' mode */
qtmux->mux_mode = GST_QT_MUX_MODE_MOOV_AT_END;
/* Require a sensible fragment duration when muxing
* using the ISML muxer */
if (qtmux_klass->format == GST_QT_MUX_FORMAT_ISML &&
qtmux->fragment_duration == 0)
goto invalid_isml;
if (qtmux->fragment_duration > 0) {
if (qtmux->streamable)
qtmux->mux_mode = GST_QT_MUX_MODE_FRAGMENTED_STREAMABLE;
else
qtmux->mux_mode = GST_QT_MUX_MODE_FRAGMENTED;
} else if (qtmux->fast_start) {
qtmux->mux_mode = GST_QT_MUX_MODE_FAST_START;
}
switch (qtmux->mux_mode) {
case GST_QT_MUX_MODE_MOOV_AT_END:
/* We have to be able to seek to rewrite the mdat header, or any
* moov atom we write will not be visible in the file, because an
* MDAT with 0 as the size covers the rest of the file. A file
* with no moov is not playable, so error out now. */
if (!gst_qt_mux_downstream_is_seekable (qtmux)) {
if (qtmux->fragment_duration == 0) {
if (!qtmux->fast_start) {
GST_ELEMENT_ERROR (qtmux, STREAM, MUX,
("Downstream is not seekable - will not be able to create a playable file"),
(NULL));
return GST_FLOW_ERROR;
}
} else {
break;
case GST_QT_MUX_MODE_FAST_START:
case GST_QT_MUX_MODE_FRAGMENTED_STREAMABLE:
break; /* Don't need seekability, ignore */
case GST_QT_MUX_MODE_FRAGMENTED:
if (!gst_qt_mux_downstream_is_seekable (qtmux)) {
GST_WARNING_OBJECT (qtmux, "downstream is not seekable, but "
"streamable=false. Will ignore that and create streamable output "
"instead");
qtmux->streamable = TRUE;
g_object_notify (G_OBJECT (qtmux), "streamable");
}
}
break;
}
/* let downstream know we think in BYTES and expect to do seeking later on */
@ -1759,50 +1886,7 @@ gst_qt_mux_start_file (GstQTMux * qtmux)
/* initialize our moov recovery file */
GST_OBJECT_LOCK (qtmux);
if (qtmux->moov_recov_file_path) {
GST_DEBUG_OBJECT (qtmux, "Openning moov recovery file: %s",
qtmux->moov_recov_file_path);
qtmux->moov_recov_file = g_fopen (qtmux->moov_recov_file_path, "wb+");
if (qtmux->moov_recov_file == NULL) {
GST_WARNING_OBJECT (qtmux, "Failed to open moov recovery file in %s",
qtmux->moov_recov_file_path);
} else {
GSList *walk;
gboolean fail = FALSE;
AtomFTYP *ftyp = NULL;
GstBuffer *prefix = NULL;
gst_qt_mux_prepare_ftyp (qtmux, &ftyp, &prefix);
if (!atoms_recov_write_headers (qtmux->moov_recov_file, ftyp, prefix,
qtmux->moov, qtmux->timescale,
g_slist_length (qtmux->sinkpads))) {
GST_WARNING_OBJECT (qtmux, "Failed to write moov recovery file "
"headers");
fail = TRUE;
}
atom_ftyp_free (ftyp);
if (prefix)
gst_buffer_unref (prefix);
for (walk = qtmux->sinkpads; walk && !fail; walk = g_slist_next (walk)) {
GstCollectData *cdata = (GstCollectData *) walk->data;
GstQTPad *qpad = (GstQTPad *) cdata;
/* write info for each stream */
fail = atoms_recov_write_trak_info (qtmux->moov_recov_file, qpad->trak);
if (fail) {
GST_WARNING_OBJECT (qtmux, "Failed to write trak info to recovery "
"file");
}
}
if (fail) {
/* cleanup */
fclose (qtmux->moov_recov_file);
qtmux->moov_recov_file = NULL;
GST_WARNING_OBJECT (qtmux, "An error was detected while writing to "
"recover file, moov recovery won't work");
}
}
gst_qt_mux_prepare_moov_recovery (qtmux);
}
GST_OBJECT_UNLOCK (qtmux);
@ -1812,28 +1896,34 @@ gst_qt_mux_start_file (GstQTMux * qtmux)
* better fine tune using the information we gather to create the whole moov
* atom.
*/
if (qtmux->fast_start) {
switch (qtmux->mux_mode) {
case GST_QT_MUX_MODE_MOOV_AT_END:
ret = gst_qt_mux_prepare_and_send_ftyp (qtmux);
if (ret != GST_FLOW_OK)
break;
/* store the mdat position for rewriting later ... */
qtmux->mdat_pos = qtmux->header_size;
/* extended atom in case we go over 4GB while writing and need
* the full 64-bit atom */
ret = gst_qt_mux_send_mdat_header (qtmux, &qtmux->header_size, 0, TRUE);
break;
case GST_QT_MUX_MODE_FAST_START:
GST_OBJECT_LOCK (qtmux);
qtmux->fast_start_file = g_fopen (qtmux->fast_start_file_path, "wb+");
if (!qtmux->fast_start_file)
goto open_failed;
GST_OBJECT_UNLOCK (qtmux);
/* send a dummy buffer for preroll */
ret = gst_qt_mux_send_buffer (qtmux, gst_buffer_new (), NULL, FALSE);
if (ret != GST_FLOW_OK)
goto exit;
} else {
break;
case GST_QT_MUX_MODE_FRAGMENTED:
case GST_QT_MUX_MODE_FRAGMENTED_STREAMABLE:
ret = gst_qt_mux_prepare_and_send_ftyp (qtmux);
if (ret != GST_FLOW_OK) {
goto exit;
}
if (ret != GST_FLOW_OK)
break;
/* well, it's moov pos if fragmented ... */
qtmux->mdat_pos = qtmux->header_size;
if (qtmux->fragment_duration) {
GST_DEBUG_OBJECT (qtmux, "fragment duration %d ms, writing headers",
qtmux->fragment_duration);
/* also used as snapshot marker to indicate fragmented file */
@ -1848,25 +1938,27 @@ gst_qt_mux_start_file (GstQTMux * qtmux)
ret =
gst_qt_mux_send_extra_atoms (qtmux, TRUE, &qtmux->header_size, FALSE);
if (ret != GST_FLOW_OK)
return ret;
/* prepare index */
if (!qtmux->streamable)
break;
/* prepare index if not streamable */
if (qtmux->mux_mode == GST_QT_MUX_MODE_FRAGMENTED)
qtmux->mfra = atom_mfra_new (qtmux->context);
} else {
/* extended to ensure some spare space */
ret = gst_qt_mux_send_mdat_header (qtmux, &qtmux->header_size, 0, TRUE);
}
break;
}
exit:
return ret;
/* ERRORS */
invalid_isml:
{
GST_ELEMENT_ERROR (qtmux, STREAM, MUX,
("Cannot create an ISML file with 0 fragment duration"), (NULL));
return GST_FLOW_ERROR;
}
open_failed:
{
GST_ELEMENT_ERROR (qtmux, RESOURCE, OPEN_READ_WRITE,
(("Could not open temporary file \"%s\""), qtmux->fast_start_file_path),
GST_ERROR_SYSTEM);
(("Could not open temporary file \"%s\""),
qtmux->fast_start_file_path), GST_ERROR_SYSTEM);
GST_OBJECT_UNLOCK (qtmux);
return GST_FLOW_ERROR;
}
@ -1963,10 +2055,16 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
}
}
if (qtmux->fragment_sequence) {
switch (qtmux->mux_mode) {
case GST_QT_MUX_MODE_FRAGMENTED_STREAMABLE:
{
/* Streamable mode; no need to write duration or MFRA */
GST_DEBUG_OBJECT (qtmux, "streamable file; nothing to stop");
return GST_FLOW_OK;
}
case GST_QT_MUX_MODE_FRAGMENTED:
{
GstSegment segment;
if (qtmux->mfra) {
guint8 *data = NULL;
GstBuffer *buf;
@ -1978,11 +2076,6 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
ret = gst_qt_mux_send_buffer (qtmux, buf, NULL, FALSE);
if (ret != GST_FLOW_OK)
return ret;
} else {
/* must have been streamable; no need to write duration */
GST_DEBUG_OBJECT (qtmux, "streamable file; nothing to stop");
return GST_FLOW_OK;
}
timescale = qtmux->timescale;
/* only mvex duration is updated,
@ -1999,10 +2092,13 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
/* no need to seek back */
return gst_qt_mux_send_moov (qtmux, NULL, FALSE);
}
default:
break;
}
/* Moov-at-end or fast-start mode from here down */
gst_qt_mux_configure_moov (qtmux, &timescale);
/* check for late streams */
/* check for late streams. First, find the earliest start time */
first_ts = GST_CLOCK_TIME_NONE;
for (walk = qtmux->collect->data; walk; walk = g_slist_next (walk)) {
GstCollectData *cdata = (GstCollectData *) walk->data;
@ -2050,12 +2146,12 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
/* tags into file metadata */
gst_qt_mux_setup_metadata (qtmux);
large_file = (qtmux->mdat_size > MDAT_LARGE_FILE_LIMIT);
/* if faststart, update the offset of the atoms in the movie with the offset
* that the movie headers before mdat will cause.
* Also, send the ftyp */
if (qtmux->fast_start_file) {
if (qtmux->mux_mode == GST_QT_MUX_MODE_FAST_START) {
GstFlowReturn flow_ret;
offset = size = 0;
@ -2077,9 +2173,12 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
} else {
offset = qtmux->header_size;
}
/* Now that we know the size of moov + extra atoms, we can adjust
* the chunk offsets stored into the moov */
atom_moov_chunks_add_offset (qtmux->moov, offset);
/* moov */
/* write out moov and extra atoms */
/* note: as of this point, we no longer care about tracking written data size,
* since there is no more use for it anyway */
ret = gst_qt_mux_send_moov (qtmux, NULL, FALSE);
@ -2091,8 +2190,20 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
if (ret != GST_FLOW_OK)
return ret;
/* if needed, send mdat atom and move buffered data into it */
if (qtmux->fast_start_file) {
switch (qtmux->mux_mode) {
case GST_QT_MUX_MODE_MOOV_AT_END:
{
/* mdat needs update iff not using faststart */
GST_DEBUG_OBJECT (qtmux, "updating mdat size");
ret = gst_qt_mux_update_mdat_size (qtmux, qtmux->mdat_pos,
qtmux->mdat_size, NULL);
/* note; no seeking back to the end of file is done,
* since we no longer write anything anyway */
break;
}
case GST_QT_MUX_MODE_FAST_START:
{
/* send mdat atom and move buffered data into it */
/* mdat_size = accumulated (buffered data) */
ret = gst_qt_mux_send_mdat_header (qtmux, NULL, qtmux->mdat_size,
large_file);
@ -2101,13 +2212,10 @@ gst_qt_mux_stop_file (GstQTMux * qtmux)
ret = gst_qt_mux_send_buffered_data (qtmux, NULL);
if (ret != GST_FLOW_OK)
return ret;
} else if (!qtmux->streamable) {
/* mdat needs update iff not using faststart */
GST_DEBUG_OBJECT (qtmux, "updating mdat size");
ret = gst_qt_mux_update_mdat_size (qtmux, qtmux->mdat_pos,
qtmux->mdat_size, NULL);
/* note; no seeking back to the end of file is done,
* since we no longer write anything anyway */
break;
}
default:
g_assert_not_reached ();
}
return ret;
@ -2257,15 +2365,21 @@ gst_qt_mux_register_and_push_sample (GstQTMux * qtmux, GstQTPad * pad,
}
}
if (qtmux->fragment_sequence) {
switch (qtmux->mux_mode) {
case GST_QT_MUX_MODE_MOOV_AT_END:
case GST_QT_MUX_MODE_FAST_START:
atom_trak_add_samples (pad->trak, nsamples, (gint32) scaled_duration,
sample_size, chunk_offset, sync, pts_offset);
ret = gst_qt_mux_send_buffer (qtmux, buffer, &qtmux->mdat_size, TRUE);
break;
case GST_QT_MUX_MODE_FRAGMENTED:
case GST_QT_MUX_MODE_FRAGMENTED_STREAMABLE:
/* ensure that always sync samples are marked as such */
ret = gst_qt_mux_pad_fragment_add_buffer (qtmux, pad, buffer,
is_last_buffer, nsamples, last_dts, (gint32) scaled_duration,
sample_size, !pad->sync || sync, pts_offset);
} else {
atom_trak_add_samples (pad->trak, nsamples, (gint32) scaled_duration,
sample_size, chunk_offset, sync, pts_offset);
ret = gst_qt_mux_send_buffer (qtmux, buffer, &qtmux->mdat_size, TRUE);
break;
}
return ret;

13
gst/isomp4/gstqtmux.h
View file

@ -144,6 +144,13 @@ typedef enum _GstQTMuxState
GST_QT_MUX_STATE_EOS
} GstQTMuxState;
typedef enum _GstQtMuxMode {
GST_QT_MUX_MODE_MOOV_AT_END,
GST_QT_MUX_MODE_FRAGMENTED,
GST_QT_MUX_MODE_FRAGMENTED_STREAMABLE,
GST_QT_MUX_MODE_FAST_START
} GstQtMuxMode;
struct _GstQTMux
{
GstElement element;
@ -155,7 +162,11 @@ struct _GstQTMux
/* state */
GstQTMuxState state;
/* size of header (prefix, atoms (ftyp, mdat)) */
/* Mux mode, inferred from property
* set in gst_qt_mux_start_file() */
GstQtMuxMode mux_mode;
/* size of header (prefix, atoms (ftyp, possibly moov, mdat header)) */
guint64 header_size;
/* accumulated size of raw media data (a priori not including mdat header) */
guint64 mdat_size;